tip-up 
adjective
1Denoting a seat in a theatre or other public place that is designed to tilt up vertically when unoccupied so as to let people pass easily.It was the first London theatre to have carpeted floors and tip-up seats and was built without pillars so that there was a clear view from every seat....
- In the 1960s, during his first football chairmanship, at Oldham Athletic, he advocated refreshment bars, executive boxes and tip-up seats.
- But unless they are pointed out beneath the tip-up seats in the Choir, most visitors to Ripon Cathedral miss the carvings made by medieval craftsmen.
1.1Denoting a rear platform of a truck or lorry that may be raised up, enabling a load to be discharged.A colleague, who was sitting with him, escaped from the tip-up lorry which rolled forward and struck a lamppost, knocking it towards a loyalist paramilitary mural near where the bar once stood.
noun North American
A device used in ice-fishing in which a wire attached to the rod is tripped, raising a signal flag, when a fish takes the bait.If you are energetic an have a second hole you can also use a tip-up....
- The lazy man's approach is to use a spring loaded tip-up but that is about as much fun as watching paint dry.