When a weft yarn travels across the warp, it takes more weft than the width of the warp. This is because the weft is actually travelling up and down between the warp threads. If you throw the shuttle across the warp, and have the yarn running straight across, when you beat the weft down into place, you will not have enough weft yarn to adequately cover the area. This will result in too much draw-in and can cause the edge warp threads to break.

The other problem that most of us have with selvages, is having loops that stick out unattractively, instead of a nice clean edge. This happens because too much weft was left out when the shuttle was thrown across. This can be corrected by a visual check and making an adjustment with the shuttle.

When throwing from the left to the right, I throw the shuttle with my left hand and catch it with my right. Then I look to see (don't touch!) if the weft yarn just thrown is just touching the outer edge of the selvage. If not, then I give a slight tug on the shuttle to pull the weft yarn into place. The right edge of the weft yarn is up at an angle almost at the reed - as in the diagram above. Then I beat, with my left hand, placing the weft into place. Change sheds and repeat the procedure working from the right.

When you weave, you may notice that one side of your work has a tendency to either have tighter edges or have more loops. This is because one side of your body is stronger than the other. You will need to be aware of this and make adjustments to your weaving as necessary to improve your weaving technique.