A ray trace analysis of the spinning prism 0-switch is presented that demonstrates that a ray may be trapped between two mirrors, one of which is rotating, for a period consistent with the pulse evolution time for a 0-switched laser. The spinning prism 0-switch therefore acts as a fast gate. The laser must be pumped hard enough for a pulse to develop within the time the gate is open. The model matches the observed spatial burn patterns of the output well and allows for prediction of the temporal pulse separation of the pulses when the laser is pumped hard. The model also implies that optimization of the configuration may be possible to match the pulse development time (evolution plus pulse width) to the total time the rays are trapped and the pulse width, which should be one-quarter of the development time. The optimization would be done by varying the rotation rate and the cavity length to achieve the match.