HOW do you block a DC layout? - Model Railroader Magazine Nov 26, 2012My question is simple, HOW do you block a DC layout so 2 locomotives or more can be operated at the same time and at different speeds and in forward and reverse with 2 power packs? Here are some details on why I need to do this: 1. I will soon have 2 locomotives, one is on order and will be here this week. 2.