Sometimes you need to get easily collapsible gusset. Use the hinge type piano, but remove the axle. There are also more simple variant — with a normal hook. The figure shows three solutions for such constipation.
SPLIT CORNER
Sometimes you need to get easily collapsible gusset. Use the hinge type piano, but remove the axle. There are also more simple variant — with a normal hook. The figure shows three solutions for such constipation.

