In the construction of drywalls, sections of drywalls are fitted together over supporting studs, a tape is applied over the joints, and several coats of a cementitious mixture are applied with a trowel over the taped joints between adjacent sections. The cementitious mixture is a sticky mass which spreads easily when troweled. The drywall itself is usually sheetrock. The problem is to smooth the cementitious mixture to provide a smooth surface (a lap-free joint). Several parallel joints present a frequent problem, and these should be finished at the same time.
At the present time, this finishing task is done with the trowel, but the work is slow and the result is inadequate because of the lap marks produced by the trowel strokes. Also, the trowel tends to remove too much of the cementitious material in the effort to get it smooth, and this leads to greater shrinkage as the cementitious material dries.