This is the USEF official diagram of measuring heel length, according to the rule book. "Heel length" may be a misnomer; what is actually being measured is hairline distance from the ground, since the heel angle can be exaggerated (high or low) and identical hair line heights may be paired to radically different heel lengths.
Received from USEF's Stacey Meier, posted here for general public information
Lexington, KY— The United States Equestrian Federation (USEF) has selected the six competitions which will be required to take heel measurements from the first and fourth place ponies in Roadster and Hackney Roadster Pony Championships. The 2008 competitions include:
J. D. Massey Classic - Pendleton, SC (April 16-19)
Des Moines Springfest - Des Moines, IA (April 24-27)
Syracuse International - Syracuse, NY (June 25-28)
Lexington Junior League - Lexington, KY (July 7-12)
Kentucky State Fair - Louisville, KY (August 17-23)
UPHA/American Royal - Kansas City, MO (November 18-22)
Prior to these show dates, competition managers, secretaries and stewards will receive informational packets that will explain all procedures and policies regarding USEF rules HK116.3. and RD112.2 which state:
“All Hackney Roadster and Roadster Ponies must be re-measured and issued new measurement cards prior to competing in licensed competitions for the year 2004 and beyond. In all Hackney Roadster or Roadster Pony championship/stake classes (except Junior divisions) at selected USEF competitions which will be notified in writing by USEF, the first place and fourth place ponies must allow a heel measurement to be taken immediately following the class to verify the heel measurement is at or below what is indicated on the current measurement card; a copy of which must be on file in the show office prior to the pony competing.
"The heel measurement will be taken by the competition steward at a location determined by the measuring official and competition management. The heel measurement must be taken from the left bulb of the left front heel, from the skin line on the lower side of the coronary band with the ruler perpendicular to the flat surface. It is the trainer's or driver's decision and responsibility to determine if the pony will be hitched or unhitched for this measurement. If the heel measurement is higher than the measurement on the pony's USEF measurement card, an overall height measurement must be performed by two measuring officials (See GR502.4) no later than one hour following the end of the session at the designated location.
"Any entry that exceeds the legal height limit will forfeit winnings in that class. In the event there are fewer than four ponies in a class, the pony occupying the final placing will be measured. In the event of an emergency and the steward is unavailable to take the heel measurement immediately, competition management must appoint a representative to remain with the pony until the heel measurement can occur.”
Any questions regarding these USEF rules or the 2008 competitions selected should be directed to Carrie Mortensen at the USEF office via email at firstname.lastname@example.org or by calling (859) 225-6986.