123 Blocks are used for many purposes. If your printer can print one accurately then you know things are going well.
This is a metric version of a 123 Block, which is 25mm 50mm and 75mm. Each hole equals 13mm which should measure half an inch. This was made in Tinkercad so it is not the most perfect 123 variation, but it is more than adequate for my purposes.
My goal is to use this to calibrate the printing accuracy of my SLA and FDM printer. Two 123 Blocks are great for levelling your gantry and if printed on the same printer they should be the same height. And with this, you can print as many as you need, make adjustments, and print again.

Creality

CR-10

No

No

200

7

Printed on SLA and FDM machines.