cpp5 = [ cpp0[0] - catch_stem_len,
cpp0[1] - (catch_stem_h + catch_cr) ];
cppB = [ 0.5*(cpp1 + cpp2)[0],
cpp1[1] - catch_pin_height - catch_knob_above_gap -
0.5 * catch_knob_dia ];
cpp5 = [ cpp0[0] - catch_stem_len,
cpp0[1] - (catch_stem_h + catch_cr) ];
cppB = [ 0.5*(cpp1 + cpp2)[0],
cpp1[1] - catch_pin_height - catch_knob_above_gap -
0.5 * catch_knob_dia ];