Answered: Pinning in trough

Pinning – A Robot is considered to be Pinning an opposing Robot if it is inhibiting the movement of an opponent Robot while the opposing Robot is in contact with the foam playing surface and another Field Element.

During a recent tournament I ref’d a Red robot was trying to descore a sack from the Blue trough. A Blue robot placed it’s arm on top of the Red robot’s arm and a stalemate occured. As I saw it Red was contacting the sack against the trough and Blue held Red. I reasoned that since the red robot’s arm was in contact with a sack, pinning did not apply. Was I correct?

A situation like the one you have described would be considered pinning. If there is contact with a sack that is in contact with field element, this would suffice to satisfy the contact requirement of pinning.