I feel like a bit of a dummy, but here goes.

I bought the Nashbar black ATB frame, and both shifters plus the rear brake are top routed cable stops. That's not my problem. My problem is the fact that the channel for the rear brake appears to be just that; a channel, with no "stop" to it. The cable housing simply runs through, with nothing to seat it against.

I've attached an image. You can see the three stops there on the top tube...the one on the upper left is the "unstopped" one for the brake cable housing.

Either this part is way defective (I hope not, I already put the bottom bracket on, and BOTH "stops" are like this) or I'm missing a part, or I need a specialized cable housing of some sort.

Any help is appreciated. Thanks.