What can I put on my window ledge to keep the wood from getting marked

A piece of white perspex

Maybe a piece of carpet, Laun, wood piece cut to fit, a piece of fiberglass cut to size!!!

they have plastic barriers at pet places to prevent claw marks but the cats can STILL go there with them on ;)

This one from Amazon works also ;)

https://www.amazon.com/Door-Shield-Pet-Scratch-Protector/dp/B0012RWDDC/ref=sr_1_17?s=pet-supplies&ie=UTF8&qid=1509130104&sr=1-17&keywords=Cat+Scratch+Guards

Something plastic, Formica on plywood, Plexiglas, stone/granite/marble cut to fit the top of the window sill plus an extra inch so the cat's claws can't reach the casing under the sill. Or, train the cat to NOT sit in the window. A spritz bottle with plain water does wonders for teaching cats to avoid places you don't want them jumping up on or scratching. My cat won't jump on the kitchen counters and I've never had any of my upholstery furniture clawed to shreds. It doesn't take but a few timely squirts with firm verbal commands to train cats to behave like civilized animals. Why put up with an animal that destroys your house? Works on dogs, too. Trimming your cat's claws, on a weekly basis, is necessary/helpful, as is providing the cat with one or more assigned scratching post inside the house, such as: a large piece of drift wood, a hefty piece of a tree limp or stump, with bark for where to sharpen his claws.

i put a runner on my long window sills! try it! heavy cloth.

I cover the sills with fabric to prevent cat claw damage.

Where in Canada are you? Anywhere but parts of Vancouver Island it freezes and melts. I would not put anything that is fabric content against the window ledge as it will attract the moisture in the winter and it will be hard to keep dry. You could get a mold growing problem.

I’m in Welland Ontario

Pat, I have the same issue, I have a big picture window brand new but the two cats love to sit on the ledges. Here is what I done for the smaller window in the living room I got a cat tower so it is at the height of the ledge the cats will now stay off the ledge and can look out the window. My thought for the big picture window, I am looking for an 4 feet old ladder which I am going to make into a tower, steps will be carpeted and will add two hammocks, the shelf that holds the paint can will be carpeted thus they can climb, sleep and get a birds eye of outside with out scratching ledge. I use a squirt bottle at times for the cats but reality is they love to look out at the birds/squirrels, perhaps a shelf just below the ledge could be added as well

I would make a wider cat sill to put over the actual window sill so that they don't have to struggle to get on and off the sill (because they will go there ) thus less likelihood of claw marks. Or put a little shelf below it, if it is too high for them to get up without clawing, that extends the width of the sill. You can use either wood or plastic, as others have recommended, and it looks like there is a little gap between the window and the top of the sill that you could use to slide a thin stabilizer for the window side, so it is less likely to tip our when they get on the edge. I wonder if you need to or want to attached it to the sill, or just use a rubber gripper (like for rugs) under it so you can remove and clean it, and make sure you are not getting water/ condensation under it.

I would put a cat shelf there.... https://www.amazon.com/s/?ie=UTF8&keywords=cat+shelf+for+window&tag=googhydr-20&index=aps&hvadid=176949442731&hvpos=1t2&hvnetw=g&hvrand=8550191007725573375&hvpone=&hvptwo=&hvqmt=e&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9033057&hvtargid=kwd-10741987915&ref=pd_sl_9g0h0fkttd_e