– The Gas cartridge may be empty (check “How do I Insert the Gas Cartridge into DDF5110500/DDF5120550 Gas Nailer” FAQ ) – The firing depth could be set too low – When setting the firing depth on the setting wheel (1): To increase: turn in direction (2), to reduce: turn in direction (3). – The nails may be too long/too short for the base material, please refer to the base material table below - Base Materials Recommended base material Recommended pin penetration Mild Steel 10mm Concrete 20mm Brick 30mm Please note fixture thickness and add above penetration – The Gas Nailer may not be pressed firmly enough against the base material - Do not hold the Gas Nailer "too loosely" in your hands. (Two handed operation is recommended) – If the Gas Nailer is defective you will need to have the Gas Nailer repaired by an authorized service agent.