However when held up to the light the thread will always appear as a solid line.

At the very top of the loop, threads of white smoke appeared.

The threads do not appear to have any practical use, least of all as fibre.

Hold the banknote against the light - the thread will appear as a dark stripe.

A thread of water appeared, then disappeared among white stones.

The thread will appear as a dark stripe when held up to the light.

Less than 30 minutes and this thread already appears to have been derailed.

Isolated threads of green appeared here and there, perhaps, but nothing else.

At Roy's house, life stops if so much as a loose thread appears on the carpet.

We could go on, but by this morning the thread appeared to have migrated into Italian, so it's over to you.