pull trough

sorry for my stupid question,but i coulden't find 'em anywere...could somebody explain me what is a pull trough?
thanks in advance..and by the way is nice to be bak

Local lingo maybe, I ask for a pull through when going negative. That is lets say I'm doing behind the neck lat pull downs; I rack on about 30lbs. more than I can handle and a buddy helps me pull the weight a bit like a spot, but I take the negative return %100. But that's the same as a spot. But uh-that's what I know it as.

Yeah difference is a spot is like for a rep or two, this would be the whole set.