This seal is normally made by holding the torch flame stationary, blowing out a hole in the main glass body to match a second tube (hose connection in this example).

The utility model discloses a burner used for quenching in hole, in particular suitable for quenching the partial surface flame in pin hole at hook tail of hook of the train.

The way this burner system melts metal is simply by pushing the flame exit port up against the hole in the furnace which ordinarily would hold the propane burner (or air blast on a charcoal furnace).