This was a first for me: As a kid picked up his alto to prepare to play an étude, his thumb rest just broke clean in half! It split in two on either side of the large screw, with both sides falling on the floor.
But the kid was still able to play, resting his thumb up against the
bottom of the chromatic F# key guard. (I told him that if he felt it
rubbing up against the metal too much, he could tape his thumb up like a
conga player might do.)