Creating a workplane aligned with a selection

To create a workplane aligned to the top of a selection:

Select some objects.
Click Workplane tab > Create panel, and choose from:
- Selection Top
- Selection Centre
- Selection Bottom
The workplane is created as follows:

For Selection Top and Bottom, the workplane is positioned relative to a theoretical bounding box around the selected objects:

Note: The bounding box is based on the active workplane.