Clicking this button will copy the shift pattern for the current view into the next one. 

Depending on your View setting for the number of weeks displayed, this will copy either 1 or 2 weeks of shift patterns.

Copy does not remove anything in the target period before it copies. If you click this button twice you would add double the number of shifts into the next view.

You may wish to use clear view to remove any unnecessary shifts before you copy a shift pattern.