A low cost method for eliminating unsightly random cracks in slabs makes use of control joints (contraction joints) and isolation joints (expansion joints). Control joints allow horizontal movement of the adjoining slabs but do not allow differential vertical movement. In other words, vertical loads on one side of the joint are transferred to the adjacent slab across the joint. By contrast, isolation joints do allow differential movement of adjoining slabs and there should be no connection across the joint. Control joints of the proper depth provide a weakened section so that cracks form below the joints where they are inconspicuous. The irregular, jagged edges formed by the crack below a hand-tooled groove or saw cut provide aggregate interlock for load transfer and avoid unequal settlement at the joint. Load transfer and resistance to vertical displacement (faulting) at control joints is needed to take care of the occasional heavy wheel load or possible differential settlement or frost heave of the subgrade. Isolation joints are required at points of potential stress- for example, around rigid objects such as manholes, drains, fire plugs, and utility poles. They are also required at intersections of walks and drives, at points where slabs abut existing buildings, steps, or curbs, and at abrupt changes in slab thickness. In contrast to control joints, isolation joints are not required at regular intervals in long drives and walks. Crack control in reinforced concrete begins with the steel. The word reinforcement as used with reference to steel in residential concrete slabs on ground is somewhat of a misnomer. Steel in quantities considered to be within the range of practical economy does not significantly increase the flexural strength of a slab on ground. Its fundamental purpose, as commonly used, is not to increase strength but rather to hold together cracks that may occur.