1/2" x 1/2" x 5/16" thick, Solid Brass with threaded holes of 4 sides and a threaded centre hole.
Meccano 5/32" threads or m 4 metric available, please choose option
As well as being used as a contruction block, this part is ideal as a nut to be driven by screwed rods to power a mechanism
 
Made in the UK