Small wooden strips are located next to each leg to keep the legs from sliding off the two by fours. These are important. You will be pushing the mount around by the legs. You do not want to be pushing the mount off the platform.
The mount is not secured to the platform by anything other than its massive weight. Perhaps it should be.
The wheels are 4" in diameter with wheel locks. When obtaining wheels for a load this size, it is important to get wheels large enough not to get stuck in cracks and on small obstructions. Don't skimp here. Get good quality wheels rated for the load.
The blocks at the end of the legs are sized to be just high enough to get the wheels off of the ground. The are necessary because the wheels will move a bit even when locked. These particular blocks were made with four sections of two-by-four plus a small section of plywood cut to size. All the spacer blocks parts were nailed together to make the block a solid unit. When lifting the ends of two-by-four to place the wheel blocks, be careful not to lift so much that you topple the mount. The mount is top heavy!
The plastic box on the base contains an AC power strip and an AC to DC converter for the mount. This stuff was placed in the box to keep it out of the dew. A hole was cut in each end of the box to allow the wires to pass through and heat to pass out. The raw edges of the holes were covered small rubber tubing. Slit the tubing lengthwise and slip it over the raw edge around the full circumference of the hole.