When one character is pinned by another character's foot.

This is not the same as stepped_on because:

• It's possible to pin without stepping. For example, pinning against a wall.
• It's possible to step without pinning. For example, if the character being stepped on is able to push the stepper away.

Not to be confused with

• stuck_to_foot - when a character is stuck on the foot without being held against another object.

See also:

• foot_on_head
• foot_on_chest
• foot_on_back
• All pinned_by_* tags
• All pinned_to_* tags