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Pulling System (TrainCraft)
Right click both carts with a Stake in your hand, it wiil say "Attaching mode on", then make them collide and it will say "Attached".
Locomotives have pulling capabilities, don't make too long trains with weak locomotives. Stats of the locomotive will be affected. (they can be seen on the top left corner when you open the locomotive's inventory. "R" by default.)
Special pull I
You can attach two locomotives together.
To do that: shift+click the locomotive you want to PULL with a Stake in your hand. Then fuel it and wait until it heats up.
Now put both locomotives in attaching mode. Then move attach them by moving one locomotive towards the other.
Special pull II
Locomotives have two states: "Can pull" and "Can be pulled".
"Can pull" means that the locomotive is able to pull any attach cart. But it can't be pulled.
"Can be pulled" means that the locomotive behaves like a cart and can be pulled by another locomotive (which is in "can pull" state).
Attached locomotives share power.