Accurate length measurement requires a calibrated lengthboard with certain features for measuring length in the recumbent position.
The critical components
of a lengthboard are 1) a fixed headpiece and 2) a moveable footpiece
which is perpendicular to the surface of the table that the length board
is on. Lengthboards are described in detail in the Accurately
Weighing and Measuring: Equipment module.
Length measurements for infants and young children should be obtained while the child is dressed in light underclothing or a diaper. The child's shoes must be removed. Hair ornaments should be removed from the top of the head.