Section 273(i) in Police Regulations, Bengal , 1943
(i)The objects actually seen by the person preparing the map including such permanent features as buildings, trees, roads, paths and tangible points connected with the case, such as blood-stains, footprints, cloth and corpse, etc., actually seen by him shall be indicated by letters of the alphabet, A, B, C, D etc., explanations of these letters being given preferably in the margin of the map, but if this cannot be conveniently done, the explanations shall be furnished on a separate sheet of paper attached to the map.
