for how long can the bridge be held down by the robot while crossing it over ??? we couldnt find anything in the game rules that limits the holding time , however we just wanted to be sure .
I do not believe there is any rule against it, however in my opinion it is not using FIRST’s spirit of Gracious Professionalism by holding it down and blocking it. Hope that helps. 
There is no rule about holding the bridge (as long as you don’t grasp, grab, grapple, etc.). Of course, you can’t touch your opponent’s bridge.