Works fine on my end, but it’s just a wiki article, so I’ll quote it:

The groma (as standardized in the imperial Latin, sometimes croma, or gruma in the literature of the republican times)[1] was a surveying instrument used in the Roman Empire.[2] The groma allowed projecting right angles and straight lines and thus enabling the centuriation (setting up of a rectangular grid). It is the only Roman surveying tool with examples that survive to the present day.[3]