Sometimes when modifying a structure, an attempt to delete a selected part of the structure requires that the non-selected bars adjoining the selected nodes are also deleted. When the Delete button is pressed (or clicking Edit menu > Clear), the following dialog displays to help you to make the right decision.
This dialog lets you decide which bars are deleted:
When selected, only the highlighted bars are removed from the structure. The node remains in the structure. The non-selected adjoining bars that meet in this node are not removed.
When selected, all the bars that meet in this node (and not only the highlighted ones) are removed from the structure. The node(s) are deleted as well.
When you click Apply, Robot deletes the relevant bars and nodes from the structure, if the second option was selected.