Hand lettered text on engineering drawings and sketches is done in engineering block.
There is a standard “font” that engineers use for all manual lettering. It's called “engineering block.”
Engineering block is ALL CAPS, roughly 5 mm (1/4 in) tall, with no risers or descenders.
Formally, it's known as Upright Single Stroke Gothic. Some examples are shown below. (Click on an image to enlarge it.)