TEXT: The GURPS Range Ruler is a tool for
  finding combat ranges on your battle map
  quickly, without counting hexes. It will
  instantly give you the attack modifier for that
  range, and also the Size Modifier for any
  object you measure on the map. (It even sports
  a handy mini-excerpt from the Size and
  Speed/Range Table on p. B550.)
  Tips on getting your money’s worth:
  1. Remember that range and size round up.
  Example: A measurement of exactly 7 yards
  is ±3; above that, up to and including 10
  yards, is ±4.
  2. At under 2 yards, the indicated modifier is a
  penalty, for size. The rules dictate a flat +0
  and no bonus for range up close – but a
  bonus is sometimes sensible (usually out of
  combat; e.g., shooting a lock at close range).
  See www.gamesdiner.com/guths.
  3. Your foe thinks he can mock your crossbow
  because the Range Ruler only goes to 10
  hexes? Think again, Pincushion. Lay out the
  ruler to its full 10” . . . and then flip it over
  for another 10”. Range identified. Twang.
  Shtuck.
  4. Want to flip the ruler a second time? Feel
  free. That’ll let you measure between 20”
  and 30”, all of which gives a modifier of ±7.
  5. You can continue flipping to measure
  greater distances, but you’ll have to refer to
  p. B550 to find the modifier. (Aren’t you
  running out of game table space by now?)
  6. Another use is as a stand to hold flying
  creatures above the battle map. Stand a
  Range Ruler vertically (use a folded but
  unglued one, or use a binder clip as a base).
  Tack on a Post-It note at the right height for
  the flier. Nifty! As long as the ceiling is set at
  10 yards, and nobody at the game table
  makes a breeze. (To find distance to a flying
  target, use another ruler or the classic
  gamers’ hack: larger of distance or height,
  plus half the smaller . . . even Pythagoras
  used that when gaming.)
  7. The Range Ruler is a mere convenience
  when you’ve got a hex map – but if you’re
  playing au naturel (without a map, silly!), it
  really comes in handy. Ditch hexes! Go raw!
  Instructions: Fold in half along dotted line and glue halves together on the unprinted side. 
  The GURPS Range Ruler was created by T Bone based on the
  GURPS speed/range rules, and is © 2009 by Steve Jackson Games.
  GURPS is a registered trademark of Steve Jackson Games.
  All rights reserved.
  
SOURCE: textdata/thevault/GURPS [multi]/GURPS - 4th Edition - Range Ruler.pdf