The arch and seat should, if possible, be clear of the spine. This is not always possible with horses possessing high withers, but it is desirable in order to ascertain the fit of the side bars. The front arch must be wide enough to admit the hand on either side of the wither.

The side bars must bear evenly on the back, or as nearly so as can be obtained. The points of the tree must be wide enough apart to clear the ribs.

The side bars must not be too long.  At this stage it is no use looking to blade bone and loin pressure; these can only hope to be avoided when the blanket and numnah are placed under the saddle.  All we can do at this stage is to make sure the edge of the side bar is not pressing into the withers or ribs, and that the arches are wide enough.

A numnah is now placed on the back, and the tree on the numnah, but without a blanket.  This manoeuvre considerably raises the saddle tree. The amount by which it is raised gives an index to the required thickness of the blanket.

It cannot be too often insisted on that a numnah or a blanket reduces the width of a front arch, and narrows the saddle across the top of the side bars.

Add numnah and blanket
The blanket is now folded, and placed on the Numnah and the tree on the blanket. The blanket and numnah are pressed up well into the front arch, and before girthing up it should be noticed whether the burrs are off the shoulders and the fans off the loins; if they are not the thickness of the blanket beneath the side bars must be increased by turning it up on either side. The girths are now pulled up and a man placed in the saddle.

The fit of a saddle can never be determined without seeing a man in it; parts may appear out of harm’s way when no weight is in the saddle, which are brought dangerously close under the pressure of a man’s weight.