gvSIG-Desktop 1.11. User manual
The Join tool combines two or more geometries from the same polygon or line layer into a single multipolygon or multiline geometry. The tool can't be used with point layers as this would create a multipoint shape, which is already a shape-independent type.
In order to use the tool the layer must be in edit mode. Use the Edit Selection tool to select the geometries to be joined, making use of the Ctrl key to select multiple geometries.
Once the geometries have been selected click the Join tool to join the geometries into a single record in the table. It should be noted that the attributes of the geometry with the higher value 'Id' will be retained, i.e. the one that is drawn last.