To obtain perfect joins, clean the inside of the fitting and the outside of the copper pipe using coarse steel wool, apply flux paste, then insert the pipe into the fitting and apply heat from a portable propane torch until a ring of solder shows at the edges of the fitting. Let the solder cool (do not pour on water) to obtain a durable weld. Yorkshire fittings are now made with lead-free solder.
The fittings come in a great variety of shapes, including types to fit taps and galvanized iron pipes.