Flat seams that are to be burnt can be either butted or lapped. In the former case a strip of clean-shaved lead is fed into the seam, and in the latter case the edge of the face lead is melted down into the under lap. For upright seams the lead is lapped; the face of the uudercloak, and the back, edge, and front of the overcloak being cleanly shaved. No flux is necessary, as, with what may be termed clean gas, free from smoke, the lead does not tarnish. A very fine flam jet is necessary, and the seam is burned from the bottom upwards by biting off a small bead of the front lead and burning it back to the undercloak. Immediately fusion has taken place the flam is quickly taken away, and then another bead is floated down to the last one; and so on until the top of the seam is reached. Overhead work is done in a somewhat similar manner, except that a very small bead is bitten off the surface of the uudercloak and floated down and fused to the face lead. Upright work is more difficult to do than flat burning, but overhead work can only be done by meu who have had considerable practice.