Embroidery hoops are a great help when repairing clothes. By stretching the worn garment over a hoop with approximately the same tension as when you wear it, you will more easily achieve a smooth and neat end result, whether you are darning, stitching sashiko, patching, or decorating.
The smallest embroidery hoops are particularly suitable for inside sleeves or trouser legs where access can be difficult. I like to unpick trouser legs when I'm doing a somewhat extensive repair. If you have a sewing machine and a good seam ripper, it's often quicker to unpick and re-sew than to fumble inside a leg.
If you are repairing with a patch as reinforcement on the inside, the patch can be slightly larger than the hoop, so you can secure it by placing it between the hoop and the garment. The extra material can be trimmed off afterwards
An embroidery hoop used for repair can be reused again and again, making it a good investment!