platform

A modular horizontal scenic unit, for the purpose of providing a variation in vertical elevation. Stock units usually measure 4'x8', the size of a standard sheet of 3/4" plywood, the most common surface covering.

One of many methods: http://www.ehow.com/video_2378394_bu...ble-stage.html .

See also the terms riser, triscuit, dais, rostrum, podium.