Cropping to the edge
If you take a full screen shot it will reach the edge of your screen in the editor and the cropping lines will not move out to the edges.
1. Click or hold down the "Size - " button to shrink your screen shot.
2. Do a rough crop of the area you want. (The crop lines now reach the edge of your reduced screen shot)
3. Click the "True Size" button and crop again accurately.