Editing > Editing Features > Adding Features

Trace Tool

You can use trace tool to add a new feature along an existing feature, for example, you can add a new line feature along an existing building as its sidewalk. To do so, click Start Editing first, and set the target editing layer which can be a line or a polygon layer. Then select the feature whose edge the new feature will be added along. For example, to add a new line feature along the building as its sidewalk, set the target editing layer as a line layer and select the building. Last, select the Trace Tool and then click on somewhere near the selected feature. An new node will be added on the edge of the selected feature, and the added line will follow the edge of the selected feature as your mouse moves, as shown in the figure below.