112 when the external dimensions of the main pipe 105 are approximately the same as or bigger than the mating hole 112 the main pipe 105 which projects axially outwardly from both ends of the through hole 102 into which it is inserted may form one continuous pipe as shown in fig7 at the same time within a circumferential surface portion thereof there is a defined connection hole 118 into which the end of a branch pipe 106 is inserted it being noted that upon the outside of branch pipe 106 engaging protrusions 115 are constructed so as to project radially outwardly and be interposed between the inside surface of the main plate 110 of the engaging body 108 and fitting body 101 these connection protrusions 115 may be formed by crimping the branch pipe 106 or by means of a separate fixed fixture each main pipe 105 respectively disposed upon the right and left sides of the joint and inserted into and projecting out from both ends of the through hole 102 and the branch pipe 106 inserted into the branch hole 103 may be independently constructed as shown in fig1 in this case the engaging protrusions 115 are also formed upon the outside of both the main pipe 105 formed of main pipes 105a and 105b and branch pipe 106 in positions adjacent to the inside of the engaging body 108 so that they engage with engaging body 108 along with fitting body 101 furthermore an o ring 104 may be disposed at predetermined axial locations and annularly about the inner circumferential surfaces of the through hole 102 and the branch hole 103 so as to provide a.