By using the Inset/Outset tool, you can find it under 'Path' underneath the boolean operators, or by using CTRL + (, CTRL + ) when a path is selected. Makes this kind of map a tad easier than it could be, however the offsets created by this tool will always be locked to a certain unit as far as I know, which makes getting the size you want a little annoying to do unless you plan ahead for it.



EDIT: I tell a lie, the other two Offset options do exactly what I said, inset/outset however will produce a new path with nodes, the other two will make a clone of the path and edit it.