I don't know if I like that name, I might change it to something else. This originally was going to be a much larger map based a bit on Colossus it kind of evolved into this. I haven't had a chance to test it. As you can see, on the bottom right, there is a ramp that goes up and doubles back. The one on the left does the same thing and they meet in the middle. You go in the door there and you can come out of the one on the right side and go up the ramp, which will lead you to the middle, or you can go to the left and it will look like the screenshot below. If you go over that little bridge there, the shotgun is there in the middle and you can go over to red base. This is right above the bridge in the above shot.
Sentinel's good enough for a name if you wanted my two cents. Screenshots are a little confusing (maybe a sketch of the layout or something?). Essentially, a modified, smaller Slayer version of Colossus?
Hopefully this explains the layout better. You can take either the left or the right on the red path, where it meets up at the blue path. The blue path splits in two. If you take the right path, it will lead up to the top where the sniper is, and if you take the left path, it will lead to where the shotgun is.