Every job practice that falls short in execution detracts from the quality of a concrete floor. Quality is established within the period between placing and final troweling. After that period of time there is little if anything that can be done to improve the floor. Where concrete arrives by buggy, chute, conveyor, or pump it will have to be moved horizontally to some extent to level the piles and fill the holes. This work should be done with a square ended shovel, concrete placer or come-along. Screeding (striking off) is the process of bringing the whole surface to the level required. This is done by long straightedges specially made for the purpose. Tamping is done only on stiff, low slump concrete. Jitterbugs, rollerbugs and other tamping devices are used after screeding to force large particles of coarse aggregate below the surface, compacting the concrete into a dense mass. The purpose of darbying is exactly the same as that of bull floating: to eliminate high and low spots and ridges left by the screed. One of these operations must be done immediately after striking off and before any bleed water has appeared. The screeding, tamping, and darbying are done- hopefully before any bleed water has appeared. Now finishers should get off the slab and let the bleed water come up and disappear before proceeding with any finishing operation. Jointers or groovers may be used to produce control joints in the plastic concrete. The bit should be at least one inch deep and able to cut one-fifth or one-fourth the thickness of the slab to ensure that a crack will form below the groove. The purpose of floating is to prepare the surface for troweling by removing small imperfections, humps and depressions, embedding coarse aggregate particles just below the surface, and consolidating the mortar at the surface. Since the perimeter of a slab usually hardens faster than the main interior area, concrete finishers often work around the edge before working the whole slab. Troweling also may be done by hand or power equipment. The troweling operation has two functions: to produce a smooth surface and to compact the surface even further making it more dense and closely packed. Curing then follows.