The idea is to mount a board on the wall (ideally screwed/bolted to each stud) that has a bevel cut into the top sloping toward the wall. Larger items such as chalkboards, easels, bookshelves, etc. can be easily mounted on the rail and locked in place and moved around without any hassle to any location in the room.
The best thing about this system is that you can create new or modify many existing items to work with it and have nearly infinite possibilities and combinations.
Step 1: The Prep Work
In my example, it is 48" from the floor to the bottom of the rail. The spacing was to accomodate the light switch in the room, but otherwise, there were no obstacles. I found that when my daughter was younger (shorter) this was a little too high for her, but she has grown into it. Mark a level line along a single wall, or all the way around the room as we did.
2.) Select materials.
I used 1/4 kiln dried Douglas fir to keep it economical. For light duty I do not see why MDF wouldn't work, but if you are going to be hanging moderate to heavy items, use a real wood or even a hardwood like oak for strength.
3.) FInd your wall studs.
I like using a rare earth magnet: it picks up the nails/screws that hold the drywall in place. I have had better results with it than the sonic stud finders and it never requires batteries.