How to move a boundary

In Normal Mode

Move the mouse cursor over the boundary that you want to move, so the cursor changes to a double-headed arrow.
Hold the left button down and drag the boundary to the desired location.

Using Edit Modes

Enter Pick and Drag mode (use the F3 shortcut key, select Pick and Drag under the Tools menu, or click the Pick and Drag Mode toolbar icon ).
Left click on the boundary that your want to move. A set of red handles will appear, one on either side of the borehole.
Move the mouse cursor over one of the two handles, hold the left button down and drag the boundary to the desired location.

Notes

When moving a boundary the depths that the boundary can be moved to are limited by the current Depth Tolerance - at small display scales (zoomed into the borehole) or with large depth tolerances the boundary will jump from depth increment to depth increment.