What are these called?

The internet has been an amazing tool for folks working on old cars, but only if you can figure out what the hell a part is called.

I don't have any pictures handy, but on my 67' Dart, there are funny little "washers" that have pie cuts around the inner hole. These are used on the ends of my heater core arm linkages and the outside of the bench seat pivots, in both cases to prevent something from sliding off a smooth steel shaft.

Just in case I ever need to try and replace them and have to source replacements, what the hell are these things called?