The advantages of using powder actuated tools (PAT) to secure light and medium weight objects to concrete and steel are indisputable. Such tools save up to 80 percent on in-place fastening costs. Their self-contained power supply makes electrical power or fuel lines unnecessary. No welders or other specialized crew members are needed to operate them. They disrupt the work very little and they get the job done faster with less worker fatigue. The main alternative to PAT fastening is drilling and anchoring. Often it is difficult to decide which system would be best. In these cases, the advice of a knowledgeable on the job site salesman, particularly one who supplies both PAT and drilling-anchoring systems, can play a decisive part. The skill of the crew member is also important. Close cooperation between the two usually results in finding the most economical and suitable fastening method for the job. PAT fastening to concrete works like thus. On a suitably designed fastener the acting forces will be distributed uniformly. When the fastener is driven into concrete, compressive reaction forces from the displaced material act on the shank and give the fastener its holding power. This takes place along the entire length of the shank except for a small cone-shaped area at the surface which cannot be compressed unless a suitable counter force is applied to support the surface. Inasmuch as fired brick or block is relatively brittle, and because the mortar joints may be highly variable in strength, it is recommended that such materials be tested in each case when fastenings must support high loads. Assuming the material is compatible with PAT, it is best to drive the fastener into the brick or block rather than the mortar joint. If possible, the fastener should be located in the center of the brick face. Should the material not lend itself to this type of fastening, the fastener can be driven into the horizontal mortar joint.