Connectivity in gEDA schematics and symbols is shown using pins, nets and buses.
Pins have a connectible end, which is highlighted with a colored swatch, and a static end. Nets can only be connected at the highlighted end.
To begin adding pins, use Add→Pin. Left-click once to position the connectible end of the new pin, and left-click again for the other end. To finish placing pins, right-click.
If you select a pin, handles will appear for each of its endpoints. You can left-click and drag these with the mouse to change the position of the pin's endpoints.
Nets are made up of straight net segments, and net connections are formed either where two net segment ends meet, or where a net segment end meets a net segment midpoint. If two net segments cross, they do not form a connection. A net connection is marked by a circular cue, and a disconnected (or “floating”) net end with a square cue.
To add a net segment, use Add→Net. There are two modes for adding nets: normal mode, and magnetic mode (the default). To switch between them, use Options→Toggle Magnetic Net.
Nets will be added using only combinations of horizontal and vertical segments, unless you hold down the Ctrl key, in which case segments at any angle will be used.
Selected nets can be modified by dragging the handles on their endpoints in the same way as pins.
Like nets, buses are made up of bus segments, follow similar connectivity rules, and can be edited in the same way.
To add buses, use Add→Bus. When adding buses, each new bus segment is constrained to be either horizontal or vertical, unless you hold down the Ctrl key. Buses do not support magnetic mode.
When you connect a net to a bus, a “bus ripper” symbol is automatically inserted. This allows two nets to be attached to the same point on a bus from opposite sides without shorting together.