Abstract: An anti-rotation clip for preventing rotation of a nut-like member (nut or bolt head) of a flanged connection to facilitate tightening or loosening of the nut-like member and eliminate the need to use two wrenches for tightening or loosening a nut or bolt. The clip is a generally L-shaped member having a horizontal portion and a vertical portion at one end thereof extending generally perpendicular thereto. A polygonal opening extending vertically through the horizontal portion has a plurality of discrete angled sides configured to surround and engage the sides of the nut-like member.