The resourcefulness surprises him, safety pins are not an item it would have crossed Bucky's mind to pick up. He did not doubt there was good reason for Steve to consider this man an ally, he is starting to see it himself.

"Alright." he agrees, flipping the knife in his hand again. Bucky turns his head, using eyes and ears both to watch out for danger.

Their vulnerability in this location makes him want to push forward regardless, but it's only a minute, he can wait. His edginess though comes across in the constant flipping of that knife, over and over until Bruce is done.