MODEL RELEASED. Screw bolt testing. Engineers testing the pulling capacity of screw bolts. The bolts have been glued into the concrete blocks using resin glue. A pneumatic load is being applied to the bolt. The stress placed on the bolt is measured and displayed on computer screens (upper right and left). Screw bolts are used in construction to attach load bearing cables to concrete supports. Therefore, the screws need to be able to withstand an enormous amount of stress.