Once you have created a site you may have some restrictions or constraints. For example a maximum height, or various boundary setbacks.
You can apply these settings to your Site via the Site Settings:
Setting a maximum height plane will immediately create a building envelope:
In the settings you can set a default setback which will be applied to all site boundaries. (Note if you have previously adjusted site setbacks manually these will all be reset)
To edit setbacks there is a specialist tool in the Edit toolbar. This works in the same way as the Vector Editor, however you are restricted to moving setback inwards and outwards. Setbacks snap to the boundary for accuracy (depending on the boundary orientation you may need to move your pencil to a site node to get it to snap exactly.)
While we are sketching and not 100% focused on the exact size of things it can be important for calculations that involve site areas to be 100% accurate.
If you change the area in the Site Settings the site you have drawn will scale accordingly so it is accurate. Very useful for small discrepancies.
Within the Display and Drawing Settings you will find a variety of options that allow you to show/hide the building envelope and setbacks.