one end of the tool set thus the chain repair tool is folded and positioned upon the tool set pull the chain repair tool 40 and the arm 50 outward shown as the imaginary line in fig3 for use get the engaging section 52 of the arm 50 away from one end of the tool set and turn the tool 40 and arm 50 in a way as shown in fig5 referring to fig6 place and position a chain in the concave room 43 rotate the housing 31 to drive the ejector pin 45 when the pin section 47 pushes up the pin of the chain joint the chain will be ready for disassembling or reassembling fig7 shows a second preferred embodiment of the present invention likewise the foldable tool set 60 also consists of a housing 62 multiple tools 64 pivoted to both ends of the housing a chain repair tool 65 including a main body 66 and an ejector pin 67 and an arm 68 as installation of the chain repair tool 65 unto the tool set 60 is the same as that of the previous embodiment no unnecessary details will be given there is no engaging section on the free end of the arm 68 in this embodiment when the chain repair tool 65 is collected on the housing 62 the arm 68 is collected altogether.