A man-portable infantry mortar in the pattern of the Stokes Mortar, the RM-40 was designed to use gas venting instead of angle of fire to control range; while this gave the advantage of being able to fire through tighter apertures, it also introduced greater mechanical complexity to the mortar, and was abandoned in later models. The main tube is fitted with a gas restriction collar at the base and a leather handgrip just below the folding bipod. The bipod is fitted with a shock absorber assembly, adjustments for traversing the mortar and leveling the legs, and a mounting point for a sight (not included), and marked "1940". The baseplate is spiked on the bottom.