The double solenoid valves will cause a pneumatic actuator to hold their position after a match has ended, but single solenoid valves might not. Single solenoid valves have a default position that they automatically (because of a spring, usually) revert to when power to the acutal
solenoid is cut. If the actuator is in the non-default position at the end of the match, and power is cut, the valve will switch Pressure and Exhaust ports, and the actuator will change states.
Basically, the way to make an actuator hold its position after the match ends is to use a double solenoid valve.
Hope this helps.
<edit>Ack, a little late. I'll leave it up, anyway.</edit>