This gauge is designed to make it painless to lay parallel tracks, evenly spaced yards, and concentric curves. The space between the uprights is designed to accept a 1/4 x 1.5 x 36 inch yardstick, or similarly sized meter stick, of the heavier sort you can find at home improvement stores, typically for under $1.00 US.
For a temporary jig, use a rubber band under the hooks to keep the gauge on the yardstick. The notch on top allows you to see the markings on the yardstick for precise positioning.
For more permanent positioning you can drill your yardstick and use a 1/8" machine screw to attach it so that it doesn't slide around - Ideal for creating a standards gauge for modular railroad systems like N-Trak or BeNdTrack. With this set you can make a jig to position tracks for a large yard, or assure proper spacing at the end of a module. The base of the jig is sized so that you can put tracks no closer than the NMRA recommended minimum spacing... though most people allow a bit more than that. You can also run a piece of 1/8 in. rod through the holes and space several tools out to be sure you're laying your track in a straight line.
Links to everything in the TrackToolz collection are below:
Z Gauge TrainToolz
N Gauge TrainToolz
HO Gauge TrainToolz
S Gauge TrainToolz
Z Track Gauge
N Track Gauge
HO Track Gauge
S Track Gauge
Track Spacers (33mm - TTrak)2-2, 1-3, 1-4
Track Spacers (1.5" inch - NTrak) 2-2, 1-3, 1-4