Two kittens adopted us several weeks ago. They are female and one is black (I named her "Bella" after my Dracula bella orchid), and the other is grey (my cousin, Linda named her "Buttercup" before I could stop her). This is their story. (No, not Linda's!)
Step 1: Tools & Materials You'll Need.
3. Marker (felt pen, etc.) if you want to mark the cloth before cutting.
4. Four safety pins.
NOTE: This is for a medium-sized cat. You will need a bigger piece of cloth and more safety pins for larger animals.
CLOTH NOTE: I have found that tee shirt material works best (not sure, but I think it's called "Jersey"). I did try another type of cloth that was more "crisp", but it failed miserably in less than a day -- it frayed and ripped, and of course the poor cat was desperately trying to lick the frayed threads. Be careful what material you use.
FASTENER NOTE: You can of course use something fancier than safety pins, but before you sew on buttons, snaps or velcro, remember that the jacket only has to last a few days - until the stitches are removed. And while it's being worn the cloth will stretch and have to be repositioned, you should look under the jacket every day to check the wound and if the jacket rips, gets soiled or has to be re-tailored you may be sorry you didn't just use quick & easy safety pins.
MOST IMPORTANT NOTE: The whole purpose of the jacket is to protect the wound and stitches from being licked or chewed. It's okay if your cat licks the cloth; no harm done. BUT IF YOUR ANIMAL BITES OR CHEWS THE WOUND AREA THROUGH THE CLOTH then you must put the head cone back on. Or possibly use a heavier cloth, or a patch of chew-proof material sewn over the wound area. So far, my cats haven't made any effort to chew through the cloth - only lick it - so hopefully you'll have the same luck.
PICTURE: Buttercup gnawing on the hated cone.
Step 2: Cut the Cloth.
So, forget your measuring apparatus for now and just "eyeball it". For a medium-sized cat you need a piece of cloth about 20" square. You need 4 holes in it for arms & legs. So, roughly mark this out with your felt pen, as shown in the picture. Now you're ready to cut, but first note the following:
In the picture the cloth is situated so the rump is nearest you and the neck is nearest the recumbent black cat. Be sure to leave 2-3 inches of cloth in front of the arm holes (i.e.: Don't get the arm holes too close to the edge).
Next, the rump. Note that the leg holes need to be CLOSE to the back edge, as close as the fabric can take it without ripping. The reason is that you don't want any cloth sticking out back there in the way when the cat has to pee or poop.
Also note that there is a lot of cloth BETWEEN the leg holes (i.e.:Don't get the leg holes too close to each other). Because here is where the cloth needs to cover and protect the abdominal incision.
Step 3: Cloth Cut.
Yes, it's crudely done & a little asymmetrical, but it does the job perfectly and it is, after all, very temporary & disposable. And the kitties seem to love their jackets.
Now, get your safety pins ready and position cat over jacket. Lower feline so front paws are in arm holes (the smaller 2 holes). When this is done, forget rear end and just pull front half of jacket up arms, wrap around snugly and fasten (safety pin) at back of neck.
Now for the hind legs. When you have the feet & legs through the back 2 holes then you just snug everything up. Use 4 safety pins, all along the spine: one near head, one near tail and 2 in between.
Make sure jacket fits very SNUGLY, but not too tight! Make sure your cat can breathe okay.
Reasonable snugness is necessary or your cat will wriggle right out of her jacket, or get 2 legs through one hole, or one arm through the collar, etc.
Step 4: Stegosaurus Impersonation.
Step 5: Surgery Well Covered.
Step 6: Finished Products.
Hope this helps someone else's pets avoid some suffering.