There are several types of saddle specialised, for example, to dressage or jumping. You are most likely to meet the general purpose saddle which is usually made from leather although modern synthetic variants are available. The saddle distributes the rider's weight across the horse's back muscles but importantly should not touch its spine which should be free from direct weight.
The tree is the foundation at the core of any saddle. The tree can be made of laminated beech plywood, plastic and fibre-glass and can be either ridged or spring tree which has a strip of flexible steel let into the tree at the waist (the front arch).
Webbing bands on which the stuffing and leather of the seat are carried are stretched along the tree. These must be neither too tight nor too loose if the seat of the saddle is to have the right dip with its deepest part in the correct place.
The tree is also the problem with many saddles. It has to made exactly symetrical and balanced else the whole saddle will be flawed. Unfortunately there are too many saddles in circulation which are fundamentally unbalanced due to mis-shapen trees and other constuction faults like stirrup bars and girth straps mounted unevenly. At best this will put the rider into a crooked position and make the horse difficult on one rein more than the other. At worst it will lead to muscle wastage, premature arthritus and behavioural problems in the horse.
A modern sythetic tree like the Sima Tree from the Thorowgood saddle range can be made to repeatable machine accuracy and overcome some of the inaccuracies in other constuction methods.
Inside a Thorowgood Saddle
The girth (a wide webbing strap) attaches to the girth straps located under the saddle flap and fastens around the chest of the horse. It holds the saddle in place.
The panel is the padding and material placed under the tree and is the part of the saddle which comes into contact with the horse.
A half panel only reaches halfway down the saddle-flap and sometimes has a large sweat-flap. Both types should be fitted with buckle guards to prevent the panel form being damaged by the girth buckles.
Panels are lined with various materials;
The stirrup leathers slide onto the stirrup bar which is just under the skirt of the saddle. These are designed such that the stirrup leathers will pull off in case of accident. Bars, which are not open-ended or are in the form of a 'D', are not safe unless worn with safety stirrups.
Numnahs are fleecy cloths placed between the saddle and the horse's back to give extra protection and to absorb sweat. Saddle cloths do a similar job though are often a 'plainer' material.
Always check the girth, straps, stirrup leathers and buckles before you mount for sign of damage.
Next - bridles.