Sheet of paper, that can be scanned or faxed. 8.5"x14" or 8.5"x11". Card stock or a blank file folder works well.
A flexible artist's curve (available at any office supply store), straightened coat hanger, or electrical wire that will hold it's shape when bent.
Masking or Painter's tape, cut into four 3" pieces and one 1" piece.
A flat surface suitable for tracing.
One or two helpers.
Make sure your horse is standing squarely on a level surface.
Find the back edge of the horse's shoulder blade (scapula). The easiest way to do this is to have someone pull the horse's leg straight forward while you rest your hand just below his wither. You'll feel the scapula slide under your hand. You can also start at the top of the shoulder and follow the curve of the scapula until you get to the rear edge.
Mark the back edge of the scapula with a piece of tape.
Measure 3 fingers width behind the horse's shoulder blade and mark with another piece of tape.
Repeat on the horse's right side.
Find the lowest spot on your horse's back and mark with another piece of tape. To find the lowest spot, lay a pencil across your horse's spine and allow it to roll to a stop.
Place the middle of the flexible cure or wire on the horse's wither, making sure that the center of the curve rests on the center of your horse's spine, and check that it's positioned correctly on both sides. Mold the curve to your horse's shape, and place a piece of tape to mark the front edge of the curve (the part nearest the mane).
Carefully remove the curve and place it on the paper. Remember which side of the curve is the horse's left and right. The easiest way to do this is to take the left side in your left hand, and the right side in your right hand.
Without changing the shape of the curve, use the black waterproof marker to trace the inside of the curve (the part that rested against your horse's back).
Mark left and right and mark this tracing #1.
Repeat steps 7-9, but this time using the lowest spot on your horse's back which was found in step 6.
Place the curve on the paper below the first tracing, and trace the inside of it with the marker. Mark this tracing #2.
Mark left and right.
Mold the curve to your horse's top line, and make little marks on the curve where it intersects with the two tape markers from the first and second tracings.
Mark this tracing #3, and be sure to note where tracings 1 and 2 were taken.
Using the ruler, trace a 2" line, marking 0, 1", and 2" so that the saddle fitter will know the scale of the drawing.