Passive robotically-reconfigurable truss structures offer considerable utility as they can quickly adjust to changing functional requirements and resources at a level of sophistication that no human builder could match. Furthermore, robot built structures can be constructed in environments such as surface of Mars or in micro-gravity, which would otherwise be too time consuming or dangerous for humans. In this paper we discuss some of the mechanical design challenges of developing a passive robotically-reconfigurable truss system, and present the concept of the factory floor, which can construct truss-like structures without climbing on them. In the proposed system, each level is constructed on a ground plane using a truss and node configuration and is elevated to make room for the next level. This process is repeated to create 3D truss structures or reversed to decompose the structure for the next task.