The BS Standards defines a range of eight Nominal heights for lettering in Technical drawingsMore..
The BS ISO Technical drawing Standard describes Five different dimension styles for us to choose from. The first two, ‘Closed – Filled’ and ‘Closed – Blank’, would usually be used in Engineering. Oblique is often favoured by Architects. I’ve never seen anyone use Open 90° or Open 30°, except when sketching by hand. There are More..