I had bought new repop seat stop bumpers many months ago, and had not yet installed them. I did not realize that the stud's integral washer needed to go "inside" the nylon/plastic piece. Well, I just did mine today. Here are the steps I used to get the studs in: I boiled the nylon/plastic pieces in a small pot of water for a few minutes, then took them out to the garage; opened the vice jaws slightly wider than the width of the threaded stud; placed the nylon piece on top of the vice jaws; put the stud through the hole, and using a large phillips screw driver (in the head of the stud) and a hammer, I pounder the stud into the nylon piece. It went in without much effort, and spins freely inside. No damage to the nylon/plastic piece, or the stud. Thanks go to Racer57 for starting this topic, and to the members who replied with advice.