I thought I would be able to follow fotofrank's excellent tutorial. But I didn't get very far. When I tried -
3. On the new blank layer, Make sure your rulers are visible Figure 1
a. To place a Guide, click and hold on the ruler while dragging it into place.
b. Place a guide a half inch from the top, a half inch from the bottom, a half inch from the left and at the 2 inch mark from the left. - every time I moved to the required length, I then released the click, and the line vanished.