A 1-2-3 block is a layout tool that can be used for both metal and woodworking. As the name suggests, the block's thickness is 1", the width is 2", and the length is 3". A quick and accurate reference to those sizes in a convenient package for all sorts of precision layout work. The block is hardened steel and the surfaces are ground to an accuracy of 0.0001" per inch.
Comes in a pack of 2
Accurate to 0.0001" per inch
Measure 1" x 2" x 3"
I'm a machinist and used these for CNC Mill set up. You can't beat these for the price. Checked with Mitutoyo QuantuMike and Linear Height Gauge, both sets I've got are BETTER than the advertized 0.0001 parallel. Only reason I gave 4 stars instead of 5 is the finish and the metal seems to be a little on the soft side. Still, a person would need to go through at least 3 sets (6 blocks) to equal the price of ONE name brand block. I would definitly recommend these to anyone with precision layout/set up needs. In fact, I gave one set to my Dad who uses them for drilling pen blanks.