Copyright Goodheart-Willcox Co., Inc. 42 Section 2 Introduction to Masonry Roller tampers serve the same purpose as hand tam- pers but cover larger surface areas. A roller tamper uses the same handle that attaches to a bull float. See Figure 3‑41. 3.3.3 Darbies A darby is a long, flat, rectangular piece of wood, alu- minum, or magnesium used to remove any high or low spots left by the screed. Darbies are usually 30″ to 80″ long and from 3″ to 4″ wide with a handle on top. See Figure 3‑42. A darby is used to float the surface of the concrete slab immediately after it has been screeded. It also helps to embed the course aggregate for later float- ing and troweling. 3.3.4 Bull Floats A bull float is a large, flat, rectangular piece of wood, aluminum, or magnesium that does essentially the same job as the darby, but enables the mason to float a much larger area. A bull float is usually 8″ wide and 42″ to 60″ long with a long handle. Figure 3‑43 shows a magnesium float 8″ × 48″ with a bracket that allows different types and lengths of han- dles to be screwed into the float very easily. Another type of bracket can be purchased where the handle snaps into the float bracket rather than being threaded. A bull float is particularly suited for outdoor use since the long handle (up to 16′) is difficult to use inside. Figure 3‑44A shows a bull float extension handle made of fiberglass that screws into the bull float bracket. This type of handle is lighter than the normal metal handle because it is made of fiberglass. The handle is not conductive, which makes it safer near overhead electrical power sources. Other types of handles instead of screwing into the bull float bracket will have a quick button attachment. All that is needed to release the handle from the bull float bracket is to push on the button. See Figure 3‑44B. Marshalltown Company Figure 3‑41. A roller tamper serves the same purpose as a hand tamper but covers larger surface areas. Stanley Goldblatt Figure 3‑42. Darbies are used to float the surface of concrete immediately after it has been screeded. Marshalltown Company Figure 3‑43. A lightweight magnesium bull float. The ends of the float are turned up slightly to reduce lines when bull floating the fresh concrete. A Marshalltown Company Figure 3‑44. Bull floats. A—Bull float extension handle is in two parts, one end screws into the bull float and the second part can be added to extend the handle when extra length is needed to float large projects. B—A bull float handle adapter. One end screws into the bull float bracket and the other end slips into the handle to allow for quick attachment and release. B