The crank length is the bend provided to the reinforcement to maintain the clear cover of the concrete structure. Generally, a maximum slope of 1:10 and a minimum length of crank of 300 mm is provided. It is also determined by the formula: Crack length = (d1 + d2 + 5) x 10 mm Where d1 and d2 are the diameters of smaller and larger rebar used to lap.