Do you need to construct a wall with
solid, filled, or sealed block tops?

Here are several reasons why you should:

 Our solution to this is Form-A-Key Cavity Cap!

 
When placed on the second from the top block, it will keep the concrete from falling into the wall so you use less concrete to "cap" the wall!

The National Concrete Masonry Association (NCMA) recommends that a solid or
filled top block be installed to distribute the loads of beams and joists.
Sealing hollow cores at or near their tops and bottom can prevent soil gas from
entering the basement, but more importantly might make the building easier to
mitigate in the event of elevated radon buildup. It is recommended for potential
radon control to seal the open blocks at the time of construction.