Download Guitar/Bass Radius Gauges

Radius gauges are a pretty handy tool to have. You can buy some from all of the usual guitar-parts suspects and they're even on Amazon (US | UK Affiliate link) these days—what an age we live in. 

Or, you can download the documents below for free. 

Print them out. Double check the sizing guides along the side to make sure they're accurate and your printer hasn't skewed anything (there's a document for US-Letter and one for A4 to help prevent and resizing issues).

Paste them to some stiff card and cut them out. 

Ta-da! Radius gauges.