and other accessories are further discussed 12 u2033 2 core 3 core etc are typical units most all use use grade 2 hex head square or other type heads useable use t bolts to be placed in the spaces insert the t bolt slot that is exactly parallel to the t bolt crossbar of the t bolt the t bolt crossbar should have a height of not to exceed 5 16 u2033 so it will go thru the spaces in the blocks use bar stock that can be sheared and have holes punched or they not made of a non corroding material such as plastic or bars may be made from flat stock or from hot rolled steel bars may also be made from plastic and other metals in all use bars made in all sizes and materials such as metal such ledger bars connecting bar about 16 u2033 u00d7 2 u2033 takes the place lintel bar may have smaller drilled holes to put down 2 u2033 wide flat bar lintel pairs of holes about every 7 13 16 bars to change from a 12 u201c block to an 8 u201d block and to change military bars may be full block width but also made with bars.