These andiron grates are built with two cross bars under the grate bars. There are 1" wide notches in the cross bars that set on top of the andiron back bar. They are all forged out of 1" solid square stock, which will endure even the hottest of fires. They help to protect the andiron back bar from deteriorating over time, and also keep the firewood away from log lighters. The width dimensions given are centerline of the notches, which will space your andirons accordingly.