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darby, derby slicker
1. A float tool used in plastering, either wood or metal, about 4 in. (10 cm) wide and about 42 in. (approx. 1 m) long, with two handles; used to float or level the plaster base coat prior to application of the finish coat, or to level the plaster finish coat before floating or troweling.
2. A hand-manipulated straightedge usually 3 to 8 ft (1 to 2.5 m) long, used in the early-stage leveling operations of concrete finishing to supplement floating.