This is a replacement part for a cat perch (aka. Kitty Condo). The original plastic insert gave out and caused the post to collapse. (Apparently, this is a common problem with these.) The original part is held in with staples, so you'll need to remove a few coils of the scratching post rope to remove the staples and the old insert. Remove the 17mm nut from the original insert and set it in the new one with a drop of glue to hold the nut in place when re-assembling the perch. I used four 3mm sheet metal screws to attach the replacement insert to the post instead of staples.