Great question, I wondered the same thing.

Tracings are meant to be sent to a fitter or saddle seller so they can use the measurements to tell you what saddles fit your horse. There are many videos that show how to measure gullet width, but gullet width alone won't give you enough information because the angle from withers to the lowest part of the back is needed so you purchase a saddle that will be level and not tipped up towards the front.

Most English saddle makers already have a stock of trees on hand, and will choose the correct one (type of tree, shape/scoop and width) for your horse. They can adjust the width, if necessary, wider or narrower by about 1 width (roughly 3/4") to match the template. If you're working with a good fitter, this part shouldn't be problematic.

My query also, but it seems many of the questions in this comment section have not been answered. Pity. My guess would be the notches along both axes are in "cm" increments?

I'd like to know the answer to this as well

@@KaraHRN me three

What's it called?

Pommel clearance is relative to the type of tree and individual conformation of the horse. For example, with hoop trees on wide horses, we talk about "adequate" clearance, which means the saddle sits in correct balance and at NO TIME comes in contact with the withers/spine. It can be 3 fingers' width, or 2, or 1. And we don't generally worry about the shoulders, as the saddle shouldn't be sitting on them - we're concerned with the tree point being at the same angle as the back, where it's resting. Without seeing the horse and saddle in question (or seeing photos), it's tough to tell what the issue is. Feel free to contact me at [email protected] if you'd like to send photos, or need more info.

Tree width (gullet plate area [fingers clearance under pommel]) and tree {point} angle (point needs to be identical angle to the shoulder blade] are different measurements. A good saddle maker and a good saddle fitter should both understand this.