L-girder benchwork is named for the inverted "L"-shaped beams which carry the load. L-girder allows tremendous flexibility in design for odd-shaped and multi-level layouts. With its open structure, it is easy to add scenery both above and below track levels. L-girder can be built with little experience and a few simple tools.
Like other types of benchwork, L-girder can be built from a variety of materials. The most common are dimensional lumber, plywood and steel. Steel studs and other components are available at many home supply stores. The techniques for using steel are similar to wood, but the materials are much less familiar to most modelers. Plywood offers greater dimensional stability and consistency at comparable cost to traditional lumber but must be ripped to proper widths on a table saw.
Whichever materials you use, you will want pieces in roughly 1X4, 1x2, and 2x4 sizes to make the L-girders, legs, cross braces and supports. Flexibility is one of L-girder's strengths, heavier or lighter construction can be used as necessary depending on your installation.