crotch reinforcement piece; saddle
A piece of fabric sewn into the crotch of pants or a garment to reinforce it; also called a saddle in tailoring. A technical term used in sewing and clothing construction.
These pants have a crotch reinforcement piece, so they are easy to move in.
When sewing on the saddle, please pay attention to the direction of the fabric.
Compound of 股 (また, 'crotch') and 布 (ぬの, 'cloth').