stage 10 trailer opposite rear wall panel 66 fig2 a c show stage 10 being erected from its closed to open configurations by a pair of bell crank assemblies 40 each bell crank assembly 40 being supported within one of support columns 34 the use of bell crank assemblies 40 overcome deficiencies in other transportable erectable stages which because of the height limitations for transportation and because of the cantilever type erection assemblies employed result in a reduced height for the stage rear wall as is seen with stage 10 rear wall panel 66 is a 34 full height 34 panel limited only by highway height limits and not by the employed erection assembly as shown for example butterfly shaped bell crank 41 has a left wing 42 and a right wing 43 bell crank assemblies 40 are hydraulically operated by a single control means not shown for example other known means can be employed to operate the bell crank assemblies bell crank 41 has a support column pivot point 46 substantially midway between left wing 42 and right wing 43 and toward the bottom 44 of bell crank 41 bell crank 41 is rotatably connected to its respective support column 34 at this location 46.