We drill and tap blind holes, usually 5-40, drill, counter-bore and mount the rib. Rifles usually require four(4) screws. Specify stock forend length. Forends are most often 13 to 16" length, while ribs are 24" length. Thus, they will fit a barrel of 37 to 40" length. Longer ribs available at extra cost. Half stock pistols require two mounting holes. Thin wall barrels require that ribs be attached with solder, call for a quote on price, due to extra preparation and cleanup.