A great question was asked by the reader The Old Gray Mare, who wanted some clarification on the triangle method. I mentioned the triangle method in my previous post "Ouch at Oak Tree." So here is a brief explanation on a quick way to check out horses.
Confirmation: Equilateral triangle method.
The triangle will follow the hip and shoulder up toward a point over the back. You want the bottom of the triangle to follow along the bottom of the barrel or stomach area. The base should be a straight line for the most part.
Using your fingers with this method means you place your pointer fingers together and your thumbs together to form a triangle...peer through the triangular hole created. It is a quick and easy way to get some ideas on the shape of a horse.
Picture: The picture holds two colors. Red is the correct triangle, and the green is the "actual" horse measurement with the triangle.
Horse 1 (left) has pretty close to an equilateral triangle proportion.
Horse 2 (right) is pretty close, but a bit longer and the base of the triangle is wider.

Thank you to my co-worker Leia for providing the picture and explaining more on horse conformation.
If you have other useful methods, tips or tricks then please do share!