1.
If you try to pin something down, you try to discover exactly what, where, or when it is.
It has taken until now to ~ its exact location...
I can only pin it down to between 1936 and 1942...
If we cannot ~ exactly what we are supposed to be managing, how can we manage it?
PHRASAL VERB: V P n (not pron), V n P to n, V P wh, also V n P
2.
If you pin someone down, you force them to make a decision or to tell you what their decision is, when they have been trying to avoid doing this.
She couldn’t pin him down to a date...
If you pin people down, they will tell you some puzzling things about stress.
PHRASAL VERB: V n P to/on n, V n P