Trim surface
To trim a scanned surface:
On the tools menu, click Trim surface 
.
Set the Brush size. Click and drag the mouse on the model to remove scan data.
Notes
Also imported scans can be trimmed.
Only the shown models will be trimmed. Use the Visibility panel to show or hide a model.
All parts of the model in the 3D viewer underneath the cursor are erased, so make sure you tilt the model in the right angle before you start trimming.
Hold down the [Shift] key to erase scan data in horizontal and vertical straight lines.
Click 
to undo the last trimming. Click 
to redo the last trimming.
Click Restore scans 
to go back to the original scans.
Click Finish.