pin down

To attach or secure with pins.

“Pin down the tablecloth, so it doesn't blow away in the breeze.”

To identify something (e.g. a decision or plan) clearly or specifically.

“Something is wrong, but I can't pin it down.”

To hold the opponent back-first so both his or her shoulders touch the mat.

To corner somebody in order to get a firm answer.

“Let's try to pin him down on a price.”