Abstract: An improved safety control mechanism for a pulley apparatus of the type comprising main support bars having at least two wheels mounted at their centers a spaced distance apart between the bars and a swing arm assembly pivotally connected to the bars at a point between the centers of the wheels, the swing arm assembly comprising a pair of arms straddling opposing surfaces of the bars and pivotally connected to the bars by a main pivot mechanism extending through complementary aligned apertures in the arms and the bars, the improvement comprising a second bolt mechanism extending through a second complementary aperture disposed in either the bars or the arms and a slot disposed in the other of the bars or the arms; the second aperture or the slot provided in the bars being disposed in the second distance between the center mountings of the wheels; the second aperture or the slot provided in the arms being aligned with the other of the second aperture or the slot provided in the bars with the arms and the bars