To provide a tool enabling the user to easily perform marking while accurately observing a draft and a tool enabling the user to easily confirm that the cut end of a pipe inserted into a socket is at right angle to the axis of the pipe during a socket welding, particularly, in a pipe repair work which is often performed in a narrow and difficult-to-work place, and also provide a method of socket welding using these tools. ソケット溶接を行う場合、特に、狭隘で作業がしにくい場所が多い配管修繕工事の中で行うソケット溶接の場合に、抜き代を正確に守ってケガキをすることが容易にできる治具とソケットに挿入する配管の端部の切断が管軸に直角になっていることを容易に確認できる治具、および、それらを用いたソケット溶接方法を提供する。 - 特許庁