From their website:
Rounding out the Terranlinx updates for Mayhem Armoury comes set #3: Mayhem Under Construction. More than just an update of the original garage, this set gives you everything you need to get “building” your buildings. Fully compatible with it’s predecessors in the modern TLX line, Mayhem Under Construction let’s you easily re-create the classic unfinished basic garage from the original Armoury set… and then keep going. With the components in this set you can create modern structures in virtually any state of progress, from steel-framed skeletons to completed buildings and any kind of renovation or expansion project in between.