I made this specific for my cat bed perch.  The cutout is made to fit my cat wall half hexagon cat bed.  This is the link to the store I ordered my cat wall bed and shelving from https://rshpets.com/en-us .   I highly recommend them!  I did a bad job installing the wall anchors and I added some better wall anchors than came with the older kit.  I'm guessing they have solved it since my kit shipped sometime in late ‘22 or early ’23.  The bed sticks out further than the other parts on my cat wall and it is higher and Murphy's law is that my cat loves it and stresses it profusely.  I am designing a clip for the top that will be crosslinked in the description below.   

I am printing these in PCTG with very similar printing settings to PETG.  Recently I've had better luck with PCTG being less hydroscopic and easier to print but pricier.  I ended up printing them with 25% infill.  I plan on using M4 hardware to mount them to the underside of the cat bed and Hillman 3 #8 Nylon Drywall Anchors for the wall side, overkill I'm sure but.  I'm installing two brackets for now.  I ended up using a long 6' 5/32 impact driver drill bit to get thru the inside of the bracket into the bottom of the bed and to mark pilot holes for the drywall anchors.  A bigger bracket would be nice but I would need a bigger printer than my Elegoo Neptune 4 Pro.

The M4 screws I currently have are too short so I am getting some more.  I stuck them in as a place holder and to prove they fit.  Also one pic shows folding the bedding pad into a hole while I was working to keep my cat off the bed.

https://www.printables.com/model/1060632-cat-perch-top-strength-bracket