[Kromm]

Those who like complications can always use the full GURPS rule, which I'll summarize here (all modifiers to hit are in addition to normal hit location penalties):

One foot of vertical difference, or less: Ignore it.

Up to two feet of vertical difference: The higher fighter has -2 to hit the feet or legs, and +1 to hit the head (skull, face, or eyes) or neck. The lower fighter has +2 to hit the feet or legs, and -2 to hit the head.

Up to three feet of vertical difference: As above, but the lower fighter is at -1 to any active defense, while the upper fighter is at +1 to active defenses.

Up to four feet of vertical difference: As above, but the lower fighter is at -2 to defend, while the upper fighter is at +2. The upper fighter cannot strike at the lower fighter's feet or legs.

Up to five feet of vertical difference: The lower fighter cannot strike at the upper fighter's head, and the upper fighter cannot strike at the lower fighter's feet or legs. The lower fighter is at -3 to defend, while the upper fighter is at +3.

Up to six feet of vertical difference: The upper fighter may only strike at the lower fighter's head. The lower fighter may only strike at the upper fighter's feet or legs. Neither gets any special bonus or penalty to attack. The lower fighter is at -3 to defend, while the upper fighter is at +3.

Over six feet of vertical difference: Combat is impossible unless the fighters adopt some strange position; e.g., the upper fighter lies down and reaches over the edge. In that particular case, he would effectively bring himself three feet closer, and his foe could strike at his head and arm.

Effects of Reach

If you have more than one yard of reach, each yard past the first brings the foe three feet closer you. This does not bring you any closer to your foe!