Other letters for the head may be definded as the need arises. V is a medium antennae insect with wings raised up and spread like a V over the abdomen like in some wasp and bees or flies. Sometimes angles close to 45 degrees present a problem. In this case one may look for where the lines of the angles intersect. K designates short abdomen with apex hidden by long wings.
D designates long abdomen with apex protruding beyond wing tips.
If you are good in guestimating wing angles of the living insect, give that value, too, to the nearest 5 degrees. Wing angles may be important in describing Diptera or Moths. It is better to guestimate wing angles to the nearest 5 degrees than to omit them all together.