I know what it is but I don't know how to explain it to other people. Could you please explain it so I may explain it to others when they ask.

The foundation lines are considered the originating bloodlines that started the breed standards. I believe in QH's Poco Bueno was considered one. Also One Eye'd Jack. But then through breeding along came other bloodlines that have created the slimmer, taller, HUS type of horses that although are still QH's, lack that old stocky heavy muscled and strong boned conformation . You know, the good 'ol cow ponies and range horses!!

Hope this helps you!!

I guess an easier way to say it might be the beginning (foundation of the breed just like a house)

EDIT - re-reading your question, I have to add that many breeders work to keep the foundation lines alive by carefully breeding within a certain lineage to keep that bloodline and type alive within their breed. This also holds very true with Morgans and the Lippincott bloodlines that made the Morgan the stocky horse they once were.

It's horses that supposedly come from the "original" bloodlines of Quarter horse. pets question and answers,www.5d2d.com

It also means TOTALLY INBRED.

Seriously.

There's thousands of horses that have to be in-bred to keep the foundation line. It's inevitable.

Like "purebred" dogs .... they are also eventually in-bred. Which is why they have so many genetic disorders compared to mutts.

So, a F QH is like a "purebred" ; dog.

They are some of the original Quarter Horses, the ones that were bred for use and work. The ones that had good bone big strong hooves and were not breaking down like these now that are bred to please the judges. Now the Judges want to see little triple 000 hooves on a 1200 lb horse, and little tiny arabish heads. So we are seeing a lot of Navicular, Ringbone, Bog Spavins, Curb, Splints in young horses because of the poor bone structure.

I have been in the horse business for many years and have never seen so much unsoundness in Quarter horses as in the last 20 years because of stupid breeding, and a lot of the are young horses.

pets question and answers,www.5d2d.com
Whimpy, King, Yellow Jacket, Clabber

Wimpy is a foundation QH King is another.