How to make the snap-hole marking template for making leash sleeves

To make the template shown above, I used a sheet of 8" square clear-plastic, .035" thick (a little thicker than 1/32". Amazon ASIN: B0CG8PLF3N). This is almost too thin. But, it's easier to cut, and less expensive to practice with (make mistakes).

I made a new template using a sheet of 1/8"-thick (.125", 8x12". Amazon ASIN: B0CQYS1RN6). That's as thick as 3.6 thin sheets stacked together. It's harder to cut, and more problematic if the drill isn't perfectly vertical (the hole will exit at a different location than where it entered). More reason to use a drill-press.

First: mark the plastic using a fine-point Sharpie pen (a traditional Sharpie is too thick.). Mark the lines to cut to get 4" wide pieces. (They can be longer than 8". That direction doesn't matter. But, they should be very close to 4" wide.). Use a T-square to draw the line across the plastic. (It's very important that the cut piece be square. Don't just mark 4" along both edges & lay the straight edge across the plastic from mark to mark. Use the t-square against one edge. If that doesn't align perfectly with the 4" marks you made, split the difference. It's less important to be precisely 4" than it is to be square.) This photo shows the thicker 8x12 plastic:

The plastic will probably have a protective film. Don't remove it yet. But, the acrylic cutter may snag it. You should use a razor blade & straight edge to cut the film along that line. You can also continue dragging the razor blade to score the plastic. That can help the cutting tool get started. But, the more you score the plastic, the more you should have the straight edge clamped down (the next step). If all you do is cut the film, you don't need the straight edge clamped down for that. You can hold that down firmly enough just for that. (If you score the plastic, don't press too hard. Start with a few light scores. That will create a track for the blade to stay in. Then you can press harder to score deeper. But still, it's better to do more medium-pressure scores than one hard one.).

Before or after cutting the protective film, firmly clamp the straight edge to the plastic using C-clamps:

Use a thin piece of wood or plastic so the C-clamp's foot (underneath) won't mar the plastic. Set the plastic on a piece of wood that's tall enough so the c-clamps are suspended freely. You want a solid, sturdy surface to press against.

For the 1/8"-thick plastic, it may be better to use a jig saw or band saw. It's very slow cutting with the acrylic cutting tool. You need to start light (like you did scoring with the razor blade above). It will enlarge the score. The deeper that cut becomes, the harder you can press to take more material. But, you can't press too hard or you'll get a rough surface inside the cut which will be hard to go over with the next cut. More passes with medium-to-hard pressure is better.

It's important to change direction every 5-6 cuts. That's because: when you start each stroke, you don't start exactly at the edge. Changing directions lets you drag the cutter through the edge which had previously been the starting edge. The edges are most prone to cracking. It's better to work more on the edges that way so they cut deeper than the middle. Also, avoid the temptation to fold it too soon (break it along the cut). It'll probably crack (and especially at the edges unless you worked harder on cutting those deeper than the rest of the cut.). I keep cutting until I can feel it coming though on the other side. Then I look more closely at the edges to make sure they're down low (they're they most vulnerable to cracking). If you get it all down low, it will fold over by itself when it's ready. You can flex it a little to test it. But, don't force it. Eventually it will "give."

After the cut is halfway through the plastic, you can remove the straight edge. The cutter should stay in the groove without the need for the guide. (The thicker plastic is hard to cut after you get to a certain depth. Removing the straight edge helps.).

If you're not handy with things like this, there's probably sellers online who will sell you 4x8" pieces (custom cut, perhaps).

Now you need to mark where to drill the holes. The very first thing to do is mark the word "top" on one side. Make that side the bottom side when you drill the holes. The side marked "top" will be the top side when you use the template to mark sleeves. The reason for this is that you're going to go to great lengths to start the hole exactly positioned. If the drill isn't perfectly straight, it will exit the other side not exactly in that same position where it started. If the top side (when drilling) faces the fabric, then the pen will contact the fabric exactly where you started the hole. It doesn't matter if the pen enters the plastic a little off.^[1]

You need these holes to be perfectly square to each other (and to the edges of the plastic template, centered within the template's edges). I drew the hole locations in LibreOffice Draw so I can print it & drill through it:

You can download that as a printable PDF (with or without dimensions shown). If you need different dimensions, you can download the source and edit that. Using a program ensures perfectly drawn holes. For some people (if they need different distances), it may be easier to draw this the old-fashioned way (graph paper & pencil). If you do that, do your best to make the dots perfectly square to each other. Photocopy your drawing before going further (you may wreck your first attempt. You don't want to have to draw it again.).

When you print the template, use a ruler to check if the printed dots are the distances they should be. Printers usually have an option to "scale to fit." See if that's enabled. (You want "100%" or "actual size").

Cut the printed template along the dashed line (which is halfway between the edge of the plastic & the centers of the holes). Cut as close as you can to the dashed line while leaving it visible. That dashed line will help you visually align & center the holes to the plastic sheet's edges. (That's important because not only should the holes be square to each other, but they should also be square with & centered within the plastic sheet.). But, don't leave too much paper. You're going to tape this to the template. If there's too much paper past the dashed line, then the tape won't adhere until it folds over the edge of the plastic. That could allow the paper to move. The tape should adhere to about 3/16" of the plastic surface, then fold over and adhere to the back of the plastic. The more front surface the tape adheres to, the less risk of the paper shifting while you work with it. (But, you need to keep the dashed line to help centering the template squarely within the plastic's edges.).

Tape the paper template to the plastic (using scotch tape). You don't want any movement. The paper should not fold over the edges of the plastic. There should be some plastic surface for the tape to adhere to before folding over the edge, and adhering to the back side too. After it's taped, treat it gently. Any movement will wreck this. Use a lot of tape to be sure.

Note: In the how-to for making the leash sleeves, I said I shrank my "adopt me" artwork 4% for printing, but not the distance between the snap holes in the y (vertical) dimension (because I don't want to change how the sleeve grips around the leash). The above paper template shows that. The x (horizontal) distance between corner snaps is 7-3/8". The quick-ref dimension is 7-3/4 (3/8 (.375)" longer). But, my y distance between snap holes remains 3-1/4" (same as thequick-ref dimension).

The diameter of the holes should match the marking pen you use. For the pen I use (discussed in the making sleeve's how-to "how to mark" section) I used a size #43 (.089") wire-size drill bit. A common 3/32" (0.094") bit would've worked. It's important to not have too loose of a fit between hole and pen. But, not too tight either (removing the pen can pull the plastic template up if the fit is too tight, causing it to move). Wire-size (or "wire gauge," or "numbered") bits give you a lot more sizes to choose from than ordinary fractional-size drill bits. Harbor Freight sells a set.

The best way to drill these holes is a drill press. You can find small (8") drill presses that aren't very expensive. (Harbor Freight sells one.). A drill press lets you put the hole exactly where it needs to be, and drill a straight hole (which is more important if the plastic is thick).

The steps are pretty simple:

1. Start with a small-diameter bit to drill a pilot hole. It could be half the diameter of the size you want to end up with, or even smaller. You could start tiny and drill a 2nd pilot hole through it (work your way up to the final-size hole. The way the hole locations are drawn on the paper template, you can see if the hole was drilled in the center. You could make corrections a larger bit. This is where wire-size bits are useful for more steps from pilot to final size.).
2. Without the drill spinning, lower the bit to the paper template. Move the plastic so the bit touches the center of the printed location.
3. Holding the plastic piece securely in place, raise the bit, start the drill, and lower it again to drill through (don't push hard. The plastic cracks easily).
4. Repeat the above for all the holes.
5. Replace the bit with one that's larger. Repeat the above.

Things to keep in mind:

• Don't press hard when drilling (the plastic will crack)
• I think a higher speed works better because the drill will melt its way through while cutting.
• Drilling a pilot hole gives you an opportunity to correct the hole position with a larger drill (if the first hole isn't centered perfectly in the paper template's dot.)
• After drilling the pilot holes, you could enlarge them with a bit half the size you want to end up at. Or, you can drill the final size. But, it's important to always lower the bit (without the drill spinning) and make sure it will be centered in the prior hole. Don't try to judge this while it's spinning. Figure it out first, then turn the press on (without moving the plastic).
• When you're done, you can lay the plastic template on another printed paper template to see how the holes align with the printed locations.