Two adjoining lines or members can be merged into one line or member. This option is available under the Delete Node function of a node's context menu, which you can call up by right-clicking the shared node.
Deleting the node with the Del key corresponds to the first option, removing the selected node and thus the connected lines, members, and surfaces. The Merge Joined Lines/Members option deletes the node and unifies the two lines or members. This option is available for nodes adjoined by exactly two lines or members.