Wraps Doesn't constrain circulation. Provides even support. Does not cut or bind the body in any way. Provides adequate support without being cumbersome. No dangling pieces that might get caught in machines or impede motion.
Machines Make sure they are well maintained.
Make sure the pin is for that machine. Make sure the seat is adjusted properly. If they are metal dumbbells, make sure they are not chipped and rusty. Don't use straight bars that are bent or unevenly balanced. Make sure all Olympic bars are properly tightened with an Allan wrench.