In direct-wound yokes, such as toroids, where individual wires are wound from end-cap to opposite end-cap along the core inner surface, the problem of layers of wire wound above and between adjacent wires forcing these wires out of place in a random manner is overcome by coating the inner surface of the core with an adhesive that increases friction and thus resists wire movement. The adhesive, applied in liquid form, remains tacky indefinitely, thus allowing turns to be removed and the parts reused if desired.