These are assets for the Level Builder addon.  For documentation of the Level Builder Addon: Level Builder  

Tips:

• Use insert and delete button to size the assets if need (When Level Builder is active). 
• You can easily scale in Z for example. (Handy for stairs or walls sometimes). You can also experiment with snapping rotation, scale and grab in Blender. See the snapping menu where you can snap on increment and use absolute grid snap. Setting shapping on like this in Blender makes it very easy to build big scenes in no-time. 
• Ever tried Workbench to render? It's super fast and these assets barely use memory so you can build really huge scenes.  
• Compatible with Group Pro addon for Blender and you can "cut" the assets right away with Box Cutter, Fluent, Speedflow etc.  
• To make an asset Single user, select it and klik on Object (menu-bar in Blender) and press: R, L, A.  
• To apply materials (colorcombinations) provided, you might want to make the plane with material Single User (Object > R,L,A) and in Edit more you select each face and press P.  It is then easier to copy material.  Note then the materials copied won't be saved unless you made the asset Single User Copy which you can then intantiate.  I will provide a video later.  
• You can see the assets also as a big collection of primitives.  After making it Single User Copy you can edit it further and still instantiate.  Interesting is instantiating collections.  

Contact:

For questions contact me on Twitter: https://twitter.com/Newmediasupply  

Soon a video will be available on my channel as well: 

New Media Supply on YouTube