The palatal bone thickness is measured at 3.0-mm anteroposterior intervals posteriorly from the middle of the distal bony margin of the incisive foramen (AP, 3–24-mm sections), and at 3.0-mm mediolateral intervals laterally from the midsagittal plane on both the right and left sides (ML, 0–12-mm sections), producing a grid pattern. The measurement site marked x is named “Left AP6/ML3.”