A method is disclosed for loading elongate wire lengths into elongate cells of a honeycomb ceramic substrate unit for a gaseous emissions treatment assembly, the cells each having a small cross-sectional area, the area shape matching the cross-sectional shape of the loaded wire lengths and marginally greater in area size than the wire lengths. A wire length is formed with a generally pointed end tip by pulling adjacent parts of a wire along the wire axis respectively in opposite directions from a desired wire breakage site. The tension and timing of the pulling operation are selected so that a desired tip profile is achieved. Initial alignment is done using machine vision. Subsequent adjustment is effected in dependence on feedback from sensors mounted close to the end of a wire insertion arm. Breakage and push insertion of wires is done using alternating gripping and moving of chucks or collets which have aperture shapes close in profile to the outer profile of the wire lengths.