[ngreen]

You can wire two singles or both side of the double or a combination of things to want activated together.

Single solenoid are either on or off so you wire it so one way the one solenoid is one the other the other is one. This is assuming the situation when you want the other off when the one is on.

For doubles you pulse one side and then activate the other side to switch. So if you wire the leads from both sides to one spike to actuate either way.
Finally if you want to activate both solenoid together I believe you can wire then together to one solenoid. It would work. Both in FWD. You couldn't power both FWD and REV together as far as I know but the other would work. And I think its legal but not certain. This would only be for something you wanted to switch at the same time.

It is better to use two spike and make a button that activates both of them with programming though.