The most popular ways of creating contraction joints is by using saw cuts, tool cuts and zip strips. The American Concrete Institute offers criteria on contraction joint construction and practices.

Look closer next time—many of them appear to hover just above the concrete, anchored by visible ... That’s critical for keeping your 30-foot pole from leaning like the Tower of Pisa.

and suspends it in a zero gravity like state, distributing the weight of the tool to the hips and ground—reducing strain on the upper body. DGH 130-22 Concrete finishing grinder (coming soon ...