The Copy option from the Points Menu allows you to copy points from models that are currently in the backcloth. This option obeys the current pick mode, so you will be asked to indicate a point in the backcloth to copy, sketch a rectangle containing the points to be copied or confirm that points that have been selected in the backcloth models are to be copied.
Note that if there is more than one model in the backcloth, all the models will be considered. Therefore, if the current pick mode is set to Rectangle, any points inside the sketched rectangle from any of the backcloth models will be copied. Similarly, for the list pick mode, any points that are selected in any backcloth model will be copied.