Part 1 of a two-part article by Paul O'Connor explaining Peter Collingwood's shaft (harness) switching technique for weft-faced rugs. It describes how floating warp threads held by doups between empty heddles on shafts 3 and 4 can be switched between pattern blocks A and B. It also gives a low-cost way to adapt a jack loom with a raised bridge, cup hooks and nylon seine twine doups, with practical sett and weft advice, and refers to Collingwood's Plate 98 rug as an example.