The safety chains are on each end of the outer plastic safety guard. and are fastened on to a fixed part of the mower on that end and the tractor on that end.. If you don't have any then your plastic guard is liable to rotate with the inner steel parts. And therefore you safety guards are not doing any good at all, and would/could wind up your loose clothing, long hair etc.
You must also grease the nylon bearing at each end of the safety shields so that the metal parts of the PTO shaft will have low friction with the outer plastic guard pieces and not break you safety chains. One thing for sure, don't come near that spinning PTO shaft.
James K0UA
The nylon bearing grease point is one of the bumps that releases the safety bell. The one that gets grease has a hole in it for a needle greaser attachment on the grease gun.