thumbpiece

A thumbpiece must be sewn on the bag at the hasp to open it by.

They were almost upon him when Kalvar Dard pressed in the thumbpiece of the bomb; they were clutching at him when he released it.

Above the handle, and attached to the lid, a metal flange or thumbpiece.

Grasp the handle, press your thumb on the thumbpiece—and presto, the lid heaves up.

He knows it will squirt if he touches the thumbpiece, but it is as liable to hit him in the face, or wet his feet as anything.