It is a very peculiar construction of a very long and narrow shape. This is why together with structure 11 it has been called the "Third Wall" of Ek Balam.

Both structures, in addition to restricting access to the central part of the site, were probably used for ceremonial purposes. This is inferred by the fact that they have stairs that lead to the interior of the square, but there are none on the outside.

It can be clearly seen that the stairs were not to enter or exit the walled enclosure for which entrances were used but to allow one or more people to go up to perform a ceremony or perhaps, they were simply used to ascend those in charge of guarding the access to through the entrances.

Structure 12 had three stages in its construction, but all correspond to the Late Classic period (700 - 1000 AD).