Other hazards (skillfully pointed out to me by my Sassy) are the under sides of cabinets. When installed, there are sometimes spaces between each cabinet unit that could allow a glider to squeeze in. Check carefully at the sides of a cabinet next to the wall where a spacer may have been placed to make the cabinet fit the space.
Use a mirror if necessary to look at the underside of cabinets along the floor for any open spaces.
I also learned there was a space under the counter at the top of my old bathroom cabinets that Sassy found to be a fun way to get into the cabinets. I covered that with duct tape until I replaced the cabinets all together.
Shower Door frames - my shower is a walk in with glass on one end and sliding doors on the front. The corner post is hollow! It is also open at the top under the header that the doors slide on. I have fleece tightly packed into that opening after having to pull Sassy out. She had her head in the hole and was trying to get into the post.
Pocket doors - mine has a bracket under the door with a 3/4 x 1.5 inch opening. Sassy got the towel away from the door one night and went under the pocket door and into the wall. I coaxed her out with some mealies but was fully prepared to knock a hole in the drywall if necessary. I now use two of the long wooden cage perches slid into the bracket under the door. These double as a space filler when the pocket door is closed during bathroom playtime. I slide them across the door opening and they fill the space under the door. They are held in place by the door frame on one side and the bracket on the other so they cannot be pushed away by a glider.