When an operation you use requires an area, it starts the Area Selection Tool. This tool starts with a point selection. It tries to automatically sweep the areas surrounding the point you showed. At this stage, right-click cancels the operation. If an area surrounding the point you showed is found, the area is selected and the process continues. If the area cannot be found, a selection dialog is opened.
You can access the same operations directly with F2 or F3 keys without the dialogue opened.
You can return to the initial state and show another point with Retry.
With this option, you must show one by one the corners of the area you want to select. Select points with Point Selection Tool (?). While selecting, you can use options such as capture modes, track another line in the coordinate calculator.
Sweep Area operation ends with by showing again the first point or with right-click or Esc.
This option allows you to select an existing area. Any Area that you can select from the screen is selected. Some objects such as Circle, Plot are also closed areas. F3 selects them and makes them used as closed areas.
"/" key must be used to select overlapping areas. In that case, objects that can be selected are listed. You can also perform this operation within the areas. In that case, surrounding areas will be listed.
Green points can be swept, red points can not be swept. As long as all supported linear objects such as line, polyline, spline, arc, spiral butt, the result is successful. Although one of the red points above seems to be closed, actually the two lines at the corner do not butt. In some cases you may have to show the same area from different places. If it is not swept but everything seems to be true, probably there are lines very close but not touching each other.