Preloaded bolts transfer the load through the contact surfaces of the plies. The contact surfaces must be prepared to achieve the satisfactory slip factor which might be determined by test or taken from tables. According to BS EN 1090-2:2008, the following table might be used to determine the slip factor for different friction surfaces. Table 1. This table applies also to packing plates provided to offset differences in thickness. It should be noted that the surface preparati