Timing belt system

Good morning, the timing belt just recently broke so I took the system apart to do the service, when I got the tire off and the bottom pulley off, I realized the then piece of metal behind the bottom pulley that holds the belt in had rotted and the piece's of which had went into the belt and that was the reason for the problem . The question is, what is the name of that part? the then piece of metal behind the bottom pulley and sits up in the timing belt cover? Because I cannot find it anywhere and I don't know if because I don't know the exact name of the part or if it's just not available?