I need a cart/dolly for my 6 foot fold up tables so I can easily roll them in and out of a closet in my shop. Something similar to the picture below. The commercial ones are too wide to fit though so I need to build one. I'm good on the frame at the bottom and plan to build it out of 2x4's and just add some 3 inch casters. I need some help figuring out the rails though. I'm thinking about 1/2 or 3/4 inch metal pipe but I don't have a pipe threader and I know I won't get exact right size pieces from a box store. Still may work something out and go that route though. My question is how do I attach the metal pipe to the wood frame?