The last ledge I built had the angle iron stolen and hammered into. So perhaps something like this would be better for longevity? Also, is it typical to get your angle iron stolen?
Someone didn't like your spot or they hate skaters so they hammered your spot and took your iron so you can't use it to make another spot. I happens a lot
Heres what you do. It can be done with angle iron upside down but you only have a thin strip to grind on. Get 2" square tube and cut it to make a rectangle the same size as the top of your ledge or box. Cut about six to ten pieces of 1/2 rebar to fit between the two longest pieces. Line the rebar to lay over the center of the holes in the block you are going to use and mark where they need to be welded to the tube or angle. Now get yourself $50 and a twelve pack of Modelo and take your parts to a repair shop or weld shop about 40 minutes before closing and ask someone if they can help you out bring groms no one can say no to groms and Modelo.
At the spot line up your blocks glue them down then put your welded to on top with the rebar lining up with the holes and drop some rebar spikes into the holes and tie them to the welded rebar with rebar wire. Now concrete it all in with the last to bags for the top having more psi or Portland cement
Pretty bullet proof but it can still be destroyed so do it somewhere where nobody cares or nobody knows
I did not proof read this so I'm sure there are some grammar mistakes and so parts that are missing an explanation but I've gotta go