The Hammer Square Lite is 4mm thick for assessing hammer verticality in tight places (like when hanging hammers), or for minimal mass when lightness matters (as when carrying it in a tool bag), or as a reference for upright hammers.
the regulating rack
Letoff racks provide letoff for a section. Regulating Racks provide the entire strike profile and change its height as needed for the whole action.
Applying The System
The Setup and Order of Operations guides you step by step and the Laminated Protocols let you tick off steps as you go, so you don't get out of order or leave something out.
The Regulating Rack's rail has LEDs that illuminate both templates and action. The Hammer Hanging Jig has its own LEDa, too. And Lighting Rails come in four sizes to shine light wherever you need it.