A set of four operating derails for protecting your O scale mainline from unattended movements.
Each derail consists of two parts: a bi-directional head and a fixed base. Installation consists of inserting a short length of wire through the pivot holes in the head and base, and then gluing the base atop the crossties of the track.
To engage the derail, simply flip the head over so that it covers on top of the rail. To disengage, simply flip the head back so that it lies in between the rails.