A narrow binding can cover a frayed edge on a woven school cuff when the cuff body is sound and the opening still fits. The binding wraps the edge and takes the wear. A stretched knitted cuff needs the knit seam guide, and a tailored cuff with an affected placket may need more than an edge repair.
Mark the damaged area and check the fastening
Close the cuff normally. Check whether the fraying is confined to the fold or reaches the buttonhole, placket or seam attaching the cuff to the sleeve. If the fastening or structure is affected, a binding over the edge will not restore it. Check the other cuff for the original width and shape. Avoid trimming until you know how much material can be lost without changing the fit.
Choose a binding that turns without a hard ridge
A thin woven bias binding can wrap a slightly curved edge. Choose a colour and weight that work with the uniform. Try a short piece over the cuff and close the fastening. If the folded stack feels bulky against the wrist or interferes with the button, try a thinner binding or get the cuff assessed. Tidy only loose strands that cannot be tucked under the binding.
Wrap the edge and secure both lips
Fold the binding around the worn edge with enough cloth on each side to catch the strong part of the cuff. Turn under the ends so there is no raw tape at the opening. Baste and check the shape on the outside. Stitch along the inside edge of the binding or sew each lip separately by hand if that gives you better control. On a machine, check the underside after a few centimetres: a line that looks straight on top can miss the lower lip.
Check wear points at the ends
Remove the basting, fasten the cuff and bend the wrist. Look for a hard corner, exposed fray or binding close enough to obstruct the buttonhole. If you repair both cuffs, compare their width and appearance before wearing the shirt.