This is a modern locomotive backshop of steel panel construction. It's designed to be flexible, serving 2, 3, or 4 tracks. At 120 feet long, it's big enough to handle almost anything, and two of most things, on each track. 

The half-roof sections are marked at each end so they may be more easily cut to fit with the configuration you want to build. Just match up the fine lines at each end and trim the sections. They are designed to be just a little large so that the roof has “eaves”. 

The long narrow strip printed under the roof section is meant to be used as a “cap” or ridgeline over the middle of the roof sections. This is meant to help seal the roof from the weather, and also serves to hide any miscut edges between the sections. It will be MUCH easier to fold if you fold it BEFORE cutting it out, then trim to fit. Since you'll have to print out two copies of the roof sheet anyway, you might want to use the second strip to reinforce the roof joint from below. 

The locomotive doors are the roll-up type. You can add to the scale look of your building by cutting out the boxes from the top of the doors on the unused sides, and gluing the pieces to layers of mat board or pieces of square styrene to build them out into a roughly square cross section. It's likely that you'll also want to cut out most of the doors so that you can actually use the building, One of the doors on the two track version is marked so that you can see what the correct size opening is. They are sized to give a 15 by 22.5 foot opening, which should be large enough even for double stacks and excess height cars in case you need to do some repair work on those as well. If you want to have even that door closed, just select the white box over it and move it to the back or delete it. To make a partially closed door, just cut out the bottom, up as high as you want it open.

Grey mat board makes a great foundation and interior floor for this building,  especially since the real one would have a cast concrete floor, Be sure to butt the mat board up against the outside of the rails, and if necessary use two pieces – the first to run up against the ties, the second to match the rail height. If you get ambitious, cut out the ties between the rails and dig a “pit” between them for your maintenance crew. If you're not so inclined, cut a piece of mat board to 7mm wide and glue it between the rails to have a solid concrete floor. You can use watercolors to add oil and grease spills to the floor.