What does "F1" key do and how to use it to spread units?

Somewhere I read that F1 helps to spread units from stack in different locations. I've tried to do that, but was not successful. Could you please tell me how to do that?

Solution 1:

The F1 key is used to select idle workers.

Recently people have used this as a trick to spread up workers under attack from various harassment:

1. Select your workers (box or ctrl click one)
2. Hit the stop key (usually s)
3. Hold down the F1 key
4. Right click to various parts of your base

Because pressing F1 only selects one worker at a time, and because giving a worker a move order makes it no longer idle (thus not selected by F1) this causes your workers to each move to a different point as you right click. For maximum spread you can even right click in a circle.