Norton Gullet Measuring Device ProA single measurement to determine the correct gullet size matching your horse's conformation. For ERIC THOMAS HYBRID and NORTON PRO saddles Step 1: For an accurate measurement, place your saddle on your horse in the correct position. On your horse's back, mark the spot at the level of the screws located under the saddle. Step 2: Remove the saddle and place the gullet gauge vertically on your mark. Step 3: Slide the gullet gauge downward until both