Here are the basic steps for making a rolled leather throatlatch for a halter. This one was sewn on a machine, but when hand sewing it is possible to hide the stitches underneath a flap made by cutting the grain with an angled channeler then gluing the flap over stitches lying in the channel. The process of rounding the strap will mushroom the edges and partially cover the exposed stitches sewn on a machine, protecting them from abrasion. That is my preference instead of cutting and gluing the grain over the stitches.
First step is to wet form a cover around the edge of a filler strip and glue it prior to sewing. This cover is bridle leather 1-1/4" wide and split to ~7-8 oz, wrapped around a 9-10 oz filler that was beveled on covered edge and the grain was roughed up prior to gluing. Most of the shaping is done with fingers, followed by some light tapping with a polished hammer to set the bond of the adhesive.

After drying overnight, the cover is sewn along the edge. I tack a piece of leather to the exposed filler strip to create a flat surface that will feed through the sewing machine without twisting.

The excess filler strip is trimmed off and the edges are beveled before shaping in a rein rounder. I usually do a bit of sanding to level the cut surface before beveling the edges. The traditional way is to scrape the cut surface with a piece of sharp, broken glass. "Glassing the edge."

After beveling the cut edges, the round is soaked in water a few minutes then sealed in a plastic bag for an hour or more to completely case the leather. A light coating of glycerin saddle soap is applied to lubricate the strap when working it in the rein rounder. It is important to work gradually, starting with a larger hole in the rounder and working down a size or two, so as not to mark the leather. The strap will take on a round profile as it is worked in the rein rounder. It is left to dry overnight after rounding.

Once the round is dry, the ends can be trimmed to 1" width and shaped around the hardware by casing the leather and clamping overnight to dry. I will cut English points/egg points on the ends and bevel the grain side After dyeing and finishing the edges, the throatlatch will be attached to the ring and a halter snap by hand sewing the returns.

Here's the finished halter that the throatlatch was made for.

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