To provide a nipple which can freely vary distance, both in vertical and transverse directions, from the adjacent pipe base by the use of only one nipple spacer.

An engagement recession 16 and an engagement projection 15 to be engaged with each other are formed on one longitudinal side surface 11, symmetrically across a center axis 11a. A pipe receiving recession 17 having a semi-circular section is formed on the other longitudinal side wall 13 which forms a hole through that a pipe of a desired diameter can be inserted, by abutting against a nipple 1a having the same shape. An engagement projection 19 having the same shape and size as those of the projection 15 on the longitudinal side wall 11 is formed on one shorter side wall 14 having the half length as that of the longitudinal walls, while an engagement recession 18 having the same size and same as those of the recession 16 on the longitudinal wall 11 is formed on the other shorter side wall 12. They are so formed that distance D2 from the corners is equalized to distance D1 between the corners and the projection 15/recession 16.