This clip is designed to hold down a standard solderless breadboard with wedge shaped rails protruding from the sides (normally used for connecting boards together or adding terminal strips). Simply print 2 to 4 of these clips, slide them on to the ends or sides of your breadboard, and screw it down onto whatever surface/housing you want to mount the board on. Uses a 4mm bolt to hold it down (4.5mm diameter hole provided). Note: As all breadboards vary from manufacturer to manufacturer, check the dimensions of your board and see if it will work with the dimensions shown in the dimensional drawing above.