DIY Cat Escape Prevention Screen | A Complete Guide to Creating Original Window Grilles to Protect Your Beloved Cat's Safety

| Before the Lattice Screen | Cats relaxing at the windowsill. On a fine day, I can open the windows without worry, enjoying the pleasant sensation of the breeze and the scents of the air along with them.

Today is February 22nd, 2026. I understand it is "Cat Day."

As someone who loves cats, I had been thinking about what I should do today. After much consideration, I decided to compile a record of the "escape prevention screens" I have built through DIY trial and error, ensuring the safety of my beloved cats and our own peace of mind.

I believe that securing the windowsills (the openings of the home) is one of the essential elements for our cats and ourselves to spend our days in safety and tranquility.

This is because the windowsill, in particular, is a vital place for them—a sanctuary where they can relax, find peace, and maintain a connection with the outside world. I consider the act of firmly protecting this space to be a very important deed in shaping a comfortable life with my cats.

Lattice Screen [1] | A self-made window grille that balances functionality with design.

Lattice Screen [2] | An overall view of the screen, featuring diagonal bracing to prevent warping.

【Table of Contents】

1）Why DIY?

2）Materials and Tools

3）Preparation for the DIY Cat Escape Prevention Screen

4）Creating and Installing the Threshold (Shikii) and Lintel (Kamoi)

5）Creating the "Lattice Screen" Fixture

6）Version Upgrades and Supplementary Points

7）Summary

1）Why DIY?

With ready-made products, it is rare for the size, design, and daily usability to all perfectly align with one's ideals. Up until now, I have been preparing spaces—from the entrance and windows to the balcony—using a combination of components from 100-yen shops and home centers, all for the sake of peaceful days with my beloved cats.

What I am introducing this time is not a simple or makeshift solution, but rather what could be called the "culmination of my cat escape prevention DIY" reached through all that trial and error.

Due to its authentic built-in construction, there are aspects that make it somewhat unsuitable for rental properties. However, I believe that by getting creative with the installation, one can find a form that suits their particular home.

Above all, I want to establish a reliable sense of security with my own hands, without compromising the tranquil life I share with my cats. It may sound a bit grand, but I hope that by sharing this record of repeated trial and error born from that wish, it might serve as a hint for living for fellow cat lovers who are troubled by similar concerns.

[CRITICAL POINTS]

● Designed for "sliding windows."

● Installation width: At least 42mm is required from the window sash frame.

-This is because the width of the threshold (shikii) and lintel (kamoi) is designed at 42mm.

-However, once you understand the contents of this article, it is possible to adjust the dimensions.

2）Materials and Tools

Materials

• For the "Screen" vertical slats: Wood: 89mm × 19mm, L1820mm | 1×4, 6ft (or 1×1, 6ft *see section 3) | 4 boards

• For the "Screen" frame and bracing: Wood: 40mm × 16mm × L2000mm (Furring strips) | 4 pieces

• For the "Threshold and Lintel": Wood: 12mm thickness | Structural plywood | 1 sheet

• For the "Stopper": Wood: Approx. 2mm thickness × 15mm width × 600mm length | Balsa wood (*see section 6) | 1 piece

• Screws: 3.3mm × 25mm | Coarse thread (Narrow shank / Slim screws) | 1 box (approx. 100 screws)

• Wood glue | 1 bottle

• Paint: Oil stain or Water-based stain | 1 can (approx. 200ml)

  • Choose your preferred color and type. The specific paint used this time is introduced in the supplementary section.

 (As needed)

• Wall anchors for screws | 1 bag (approx. 20 pieces)

• High-strength outdoor double-sided tape | 1 roll

Tools

• Finishing: Sandpaper (#60–80 grit), Cloth | 2–3 sheets (Sandpaper)

• Measuring: Measuring tape (Steel convex tape), Pencil, Eraser, Ruler (approx. 30cm)

• Processing & Fixing: Saw, Screwdriver, Clamps | 5–6 pieces (Clamps)

  
  

(Useful to have)

• Random orbit sander

• Electric screwdriver

• Electric drill (for pilot holes)

[CRITICAL POINTS]

● It is crucial to choose wood with as little warping and knots as possible. -Warping leads to distortion, and knots can cause the wood to crack during processing.

● Wood (Furring strips, 40mm × 16mm) is used for the frame of the "screen."

-The threshold (shikii) and lintel (kamoi) are designed to match the thickness (16mm) of these furring strips.

● It is best to set the groove width of the threshold (shikii) and lintel (kamoi) to about +2mm relative to this thickness.

-*In this case, the design size for the groove width will be 18mm (16mm screen frame thickness + 2mm). (See section 3(1))

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(Supplement: Terminology & Explanations) *Note: You can skip this section if you wish. This is for supplementary information.

・1x4 (One-by-Four): 19mm x 89mm. A standard lumber size commonly used in DIY. The 6ft (approx. 1820mm) length is common and cost-effective.

• 1x1 (One-by-One): 19mm x 19mm. Available in the same lengths as 1x4.

• For Furring (Dobuchi): Lumber for underlying structures available at home centers. While "approx. 45mm width x 20mm thickness" is a common standard, I used 40mm width x 16mm thickness for this project. It comes in varieties like Cedar (light and soft) or Red Pine; either is fine. Don't feel restricted by the term "for furring"—the key point is simply to use lumber with these specific dimensions.

• Threshold (Shikii): The bottom rail. The groove is shallow. Typically 3mm–4mm deep; designed at 5mm for this project.

• Lintel (Kamoi): The top rail. The groove is deep. Typically 12mm–15mm deep; designed at 13mm for this project.

• Diagonal Brace (Sujikai): A structural reinforcement member installed diagonally to prevent warping and distortion.

• Structural Plywood: The standard size is 910mm × 1820mm. Use 12mm thickness (9mm is also fine). Structural plywood is recommended over regular plywood as it is manufactured with consideration for formaldehyde levels. Since it will be cut down for use, there will be plenty left over, but it remains very cost-effective.

• Balsa Wood: A soft, thin wood that can be processed with a utility knife. Often used for craft models and similar projects.

• Coarse Thread Screws (Slim/Narrow Shank): Common screws used for wood. If you change the thickness of the lumber, choose a length accordingly. While diameters like 3.8mm and 4.2mm are mainstream, I strongly recommend using "Slim/Narrow Shank" screws (3.3mm diameter) to reduce the risk of the wood splitting.

• Sandpaper: The lower the grit number, the coarser the texture. For this project, #60–80 grit is easy to work with. Using a sander (especially a random orbit sander) will make the work go much faster.

• Convex Ruler (Tape Measure): A steel retractable measuring tape.

• Saw: I recommend the "Z-saw / 7-sun-me" (approx. 210mm tooth length), as it makes processing wood very easy. Since these use disposable replacement blades, if you're buying new, look for a set that includes the handle.

• Paint: I used "Watco Oil (Made in UK)." Since it's applied and then wiped off with a cloth, it's hard to get uneven patches and feels great to the touch once dry. It's a plant-derived product based on linseed oil, so it's cat-friendly and highly recommended. The color used this time is "Dark Walnut."

• Clamps: Tools used to hold pieces together while the wood glue dries. These are also available at 100-yen shops.

• Wall Anchors: Various types of anchors are available. These should be used when installing a "Kamoi" (door header) on gypsum board or drywall where standard screws cannot provide sufficient grip. (For the screws being used this time, products such as the "AX / F-Plug / F5-25B" or "Dandori Vis / Kabe-Pita! Mini" are recommended for their ease of use.)

• High-Strength Outdoor Double-Sided Tape: I recommend the outdoor version as it is weather-resistant.

• Electric Drill: Used for drilling pilot holes. Drilling a pilot hole is effective in preventing the wood from splitting when the screw is driven in.

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3）Preparation for the DIY Cat Escape Prevention Screen

It will make the process much smoother if you have the wood cut to the following dimensions using a home center's cutting service.

Material [1] | 1x4 lumber cut lengthwise into 4 equal strips. The photo shows enough for 2 boards (8 strips).

1) Cut the "Structural Plywood" in the longitudinal (1820mm) direction:

・18mm width: 7 pieces

　-(Breakdown: 3 for the threshold, 1 for the lintel, 2 spares, 1 for the window brace *see section 6)

・25mm width: 4 pieces

　-(Breakdown: 2 for the lintel, 2 spares)

2) Cut "1x4 lumber" lengthwise into 4 equal strips:

・16 pieces (from 4 boards)

Note: Some home centers may refuse lengthwise (rip) cuts on their panel saws. It is safer to confirm if this service is available before making your purchase.

Note: For the smoothest experience, you can simply purchase the required number of 1x1 pieces (19mm square) from the start.

(Reference Section 6: For a total width of 860mm with a 30mm spacing layout, 15 pieces of 1x1 are also sufficient.)

4）Creating and Installing the Threshold (Shikii) and Lintel (Kamoi)

Construction [1] | Creating the Threshold and Lintel. By combining the pieces cut from structural plywood, you create the "grooves" necessary for installing and removing the screen. The top is deep, and the bottom is shallow. This simple structure ensures both smooth movement and prevents the screen from falling out.

1) Measure the total width of the window (e.g., 1725mm). 2) Threshold (Shikii): Assemble three 18mm-wide pieces into a "U-shape" and bond them with wood glue. 3) Lintel (Kamoi): Sandwich one 18mm piece between two 25mm pieces to form a "U-shape" and bond them. 4) Fix with clamps and wipe off any excess glue with a cloth. 5) Once the glue is dry, cut the rails to match the window width, sand them, and apply the finish (oil/stain). 6) Secure them to the window frame with screws (use anchors or high-strength double-sided tape if necessary).

Material [2] | Secure firmly with clamps in several places. Any glue squeezing out inside the grooves will obstruct the movement of the screen, so be sure to wipe it off thoroughly before it dries.

Installation [1] | Mounting the Threshold and Lintel. As shown by the red lines, ensure that the top and bottom grooves are perfectly aligned vertically before securing them.

[CRITICAL POINTS] Installation Cautions

● Alignment of Threshold and Lintel: Install them perfectly vertical to one another to prevent misalignment.

Tip: Using the window sash as a reference and placing wood blocks of the same thickness against it at the top and bottom during installation helps ensure they align correctly.

● Maximum Gap of 3cm:

Ensure the gap between the screen and the window is no more than 3cm. If the gap is too wide, kittens or small cats may be able to squeeze through and escape.

● Do Not Swap the Threshold (Bottom) and Lintel (Top):

Remember: The threshold is the one with the shallower groove.

5）Creating the "Lattice Screen" Fixture

1) Width: Measure the window frame and match the width of one side of the window (e.g., 860mm). 2) Height: Measure the inner distance (effective vertical dimension) between the installed threshold and lintel (e.g., 1018mm). 3) Cut the "for furring" lumber (40mm x 16mm x 2,000mm) to the required sizes.

• For Horizontal Frames: Length = 860mm... 2 pieces (Top & Bottom)

• For Vertical Frames: Length = 998mm... 2 pieces (Left & Right)

• For Diagonal Brace: Length ≈ 1300mm... 1 piece

Construction [2] | Determining and Adjusting the Vertical Size of the Screen. This "minus 20mm" clearance is the key point that makes on-site adjustments so easy.

[CRITICAL POINTS]

● Set the vertical frame length to "Effective Vertical Dimension minus 20mm."

-This is the biggest advantage of this design. By constructing the frame this way, you can adjust the total height of the lattice screen by approximately 1mm to 15mm to match the effective dimensions. This allows you to absorb slight measurement or construction errors, making it much easier to avoid critical failures.

-I've summarized the tips for determining and adjusting the overall vertical length of the "screen" in the diagram. Please refer to it as well.

● Assemble the main frame of the screen and temporarily secure the four corners with screws.

● Actually place the screen into the threshold and lintel to check the movement and make fine adjustments.

● Slide the "screen" to one side while it's in the tracks, and secure the frame once the vertical gap is eliminated.

-This is another point I highly recommend. Achieving perfect horizontal and vertical alignment for fixtures is a difficult task even for professionals. However, with this "custom-fit on-site" method, you can match even the subtle tilts of your house's walls. This makes it easy to achieve a beautiful, gap-free finish right up to the edge.

4) Install the vertical slats inside the frame at a pitch of approximately 30mm, and add the diagonal brace (sujikai).

-The diagonal member prevents distortion and stabilizes the entire structure.

5) Sand the surfaces and apply the finish (oil/stain) to complete the project.

Construction [2] | Installing the Vertical Slats and Securing the Diagonal Brace. By using 30mm wood offcuts as spacing guides, you can nail the slats at even intervals. Reinforcing the back with a diagonal brace ensures a sturdy, distortion-free screen.

6）Version Upgrades and Supplementary Points

・Gap Prevention Measures (Window Sash):

To fill the gap between the window sash and the "screen," attach a reinforcement piece (the same material used for the furring) to the back of the lattice frame.

-This is especially effective if you are concerned about gaps or if you have a small kitten.

Version Upgrade | Security Locking Bars for Safety and Peace of Mind. This system uses offcuts and spare materials to physically prevent the screen from sliding or the window from being opened. It significantly reduces the risks associated with a cat's unpredictable behavior.

・Installing the Window Locking Bar (Opening Side): For added peace of mind, it is recommended to secure the window so it cannot be opened by your cat.

１) Prepare the Bar: Cut an 18mm structural plywood piece to match the width of the window opening, then sand and apply the finish (oil/stain).

2) Installation: Place it directly into the window frame's track to block the sash from moving. (A tension rod can also be used as a substitute).

-This method is highly convenient, as you simply remove the bar whenever you need to open the window yourself.

・Installing the Screen Locking Bar (Non-screen Side): The screen itself has some weight, but adding a locking bar provides extra security.

１) Measure and Cut: Measure the width of the side without the screen and cut the furring lumber to size.

2) Assemble: Glue a strip of balsa wood along the longitudinal center of the lumber using wood glue.

-The balsa wood will fit perfectly into the groove of the threshold, keeping the bar securely in place.

3) Finish: Sand the surfaces and apply the finish (oil/stain).

[Version Upgrade] Extra Steps for Safety and Peace of Mind

Even if the lattice screen itself is perfectly built, there remains a concern that a cat might use brute force to slide the screen or the window open. To address this, we can create "Locking Bars" (braces) using leftover wood scraps.

The key to the Screen Locking Bar is attaching a strip of balsa wood (or similar material) to the underside so it meshes with the threshold groove. This prevents the bar itself from shifting and significantly reduces the risk of the screen sliding unexpectedly due to a cat's strength. Note: However, a cat's persistence and ingenuity can sometimes lightly leap over our wildest imaginations. No matter how foolproof we believe a setup to be, it's important not to be overconfident. True safety and peace of mind come from occasionally double-checking everything with human eyes.

7）Summary

For those who aren't accustomed to woodworking, this project might take a bit of effort. However, I encourage you not to strive for perfect precision, but rather to embrace the process with a relaxed mindset and enjoy the craft itself. I’ve found that even if a few awkward spots remain, they become the "character" of handmade work—a tangible part of the memories woven into your home. Above all, there is profound meaning in the challenge of personally shaping a safe and peaceful life for your companions.

While I’ve used the practical title "Cat Escape Prevention Screen," the lattice installed by the window is by no means a "cage" to lock them in. Instead, it is a "boundary" designed so that we and our beloved cats can relax together. That is why I hope this space is not only functional but also a place of comfort.

Watching the light filter through the finished slats and seeing the quiet shadows fall upon the floor—and catching sight of them lounging peacefully within that scene—makes me feel from the bottom of my heart that preparing this space was truly worth it.

Although this guide focused specifically on windows, these principles can be applied to any "boundary," such as entrances or balconies. I hope to introduce specific examples for those areas on another occasion. I would be honored if this article helps enrich your life with your precious partners and serves as a small aid in nurturing many calm and happy days ahead.

[For more on my personal philosophy regarding these "boundaries," please read here.]

| In the Sunbeams | Light filtering through the lattice, quiet shadows falling across the floor. My beloved cat relaxing in the midst of it all. This is a time more precious than anything else.