I made patterns in accordance with measurements of wrist perimeter and perimeter 8cm above wrist.
The first step: eight centimeters height, two perimeters laid as widths, all joined in trapezium.
Step two: room for velcro. Four lines perpendicular to the basic ones. I prolonged them on the left for 2 cm.
A bunch of lines for those who don't own a curve:-D You can spot two horizontal lines at the point a vertical supporting line meets lines from step two. Short lines at the break to smooth the pattern.
Tiny lines finish the curve. You can see well now the symmetrical pattern with two cm added for the velcro.
I cut four pieces (all different - two wrong and two right sides) and marked position of velcro.
Ironing these wasn't very comfortable as the pattern was drawn inside. Steam helped a lot to deform the curved edges.
I sewed on 8 x 2 cm velcros by zigg zagg stitch. I think it's a lot tighter than just straight stitch.
I took two matching pieces (cut the edges to minimum) and sewed them together two milimeters along the edge. That's all:-)
