Face or edge jointing? in theory, you shouldnt apply any pressure to either operation. Adding pressure, especially face jointing could deform the board causing an irregular face when the piece is at rest, and you would never get it flat. I typically try to simply allow the piece to rest on the infeed table and push it through from the trailing edge. edge jointing on the other hand isnt as prone to deformation as face jointing unless youre doing narrow boards or soft woods and then the same rules apply as face jointing for me.