Was just playing NW as an engineer. The way you select what you want to build is by right clicking while using the hammer.
It would be nice if you could preselect what you want to build before you place the construction site. Great way to stop trolls and people that don't really know how it works from fuck it up on you. It can be really, really lame getting your site jammed with crap. Even worse when its on strat and you don't have a gushing fountain of them to replace your failed experiments.
