Abstract: The present invention provides an open-close device, including a first member, a second member, a third member and a fourth member; the second member is rotatably connected to the first member, the third member is rotatably connected to the first member, the fourth member is rotatably connected to the second member and rotatably connected to the third member; the open-close device further includes an angle adjusting device which is provided at a joint between the third member and the first member, for adjusting the bending angle of the third member with respect to the first member.

Abstract: The invention discloses a utility knife, including at least a utility knife body, which has a first end part and a second end part; the first end part is arranged with a first mounting bracket, and the second end part is arranged with a second mounting bracket. A first blade is arranged detachably on the first mounting bracket; a second blade is arranged detachably on the second mounting bracket. Users can select appropriate blades to work during operation, or alternatively use different blades to operate without replacing blades. When a blade on one end becomes non-serviceable, users can immediately switch to use the blade on the other end to continue operation, which prolongs the time of continuous work and enhances the efficiency.