These are Euro style terminal blocks.
Each two place block has a screw hole for easy mounting. Use a small blade type screw driver to install wire. For wire sizes from 28 to 16 gauge. These small blocks are perfect for use with igniters and altimeters. You can rapidly swap fresh igniters for decreased turnaround time. Keeps things organized in the avionics bay!
They also make great mechanical attachments for nichrome wire applications, especially hot wire foam cutters. This is what we use in the shop for our 26 ga NICR hotwire bow cutter, along with a 110v Variac and a foot pedal rheostat.