The included hardware is a plastic angle clip similar to the one banjoflyer posted above. Both holes are elongated for adjustment. Along with the angle brackets, they supply 1/2" long, Phillips, pan head, sharp pointed screws that are self drilling into wood, no plot holes required. The assembly instructions show where to locate them which is on the legs, then you fasten them to the plywood top. You can install these on the legs before installing the top, then you only have half the amount of screws to install from below. You can also position the brackets even with the top of the leg and framework to insure the top is held tight to the framework.
All fastening of the 1/2" (or larger) plywood top is done from below the layout, not down through the top. This allows you to take it apart at a later time (if you ever re-locate) with minimal disruption to the items, track, buildings, scenery or whatever you have fastened to the top during the construction of your layout. It is a very well designed and thought out system.
Yeah, I'd just echo what rtr12 has mentioned. I put mine together a while ago and as I recall it was pretty easy. Although I did not put the bracket clips on the legs before the plywood top which is actually a good suggestion now that I think about it. It's a little tight working in the corners underneath but very doable.
I had an issue of two pieces of plywood not really fitting together snugly where they met at the "seam" so I took some small wood screws and carefully put them in from the top to get a tight and secure fit. Worked fine. Just have to be careful when drilling in from the top. I only used two I think.
