collapsing chair

Problem, dear readers ... actor sits on chair, carries chair around ... then ... again sits on chair, which 'collapses' with broken leg, casting actor to the (stage) floor. Actor demonstrates this by holding chair aloft, broken leg dangling. General business, hubbub, actor goes up/off stage, SFX of hammering and actor re-appears with 'repaired' chair. Night after night.
Any ideas?