Can't Constrain LInear Slide in Solidworks

I can’t for the life of me figure out how to constrain the linear slide assembly to allow it to, you know, slide, but still fit meshed together… How do I do this? Better yet, want to send me a Solidworks file?

What I did in Inventor was to place a mate constraint with a distance of 0.402 inches between top and bottom part inner surfaces and then add a flush constraints between two surfaces on the square holes. Here a pic, it’s hard to show the flush constraint so I just added a work surface to show where the holes are constrained. One of the two parts then needs to be constrained to something else or grounded so the other can move with respect to it. I assume you would do more or less the same in solidworks.

I have no idea why that didn’t work for me before. I think I was tying the endlines together instead of the top and bottom surfaces. Thanks!