When the mocs are sewn, the upper wants to be placed the right way on the sole. The tip of the upper and sole should match up. The two wings of the upper should be the same distance down the side of the sole, and should stick out the same distance from the edge of the sole. While making my first several pairs of mocs, I tried in vain to fit upper to sole by guessing. The upper was always skewed in some way, tilted toward the right or left.
A common technique in sewing is to dart two pieces of material together. They’re attached at intervals along their length, either with pins (for fabric), or with stitches (mocs), so that they don’t slip and slide relative to one another when sewn. With mocs, I placed darts by sewing the upper and sole together at every 10 or so holes on the sole.
To start, darts were placed at three points – the tip and each wing of the uppers.
Next, darts were added every 10 or so holes along the sole.