A Philadelphia rod consists of two sliding sections graduated in hundredths of a foot.
The division of the device in two sliding sections are devised for ease of transport.
The rod must be fully extended, when higher measurements are needed to avoid reading errors.
When the target is equipped with a Vernier scale measurements to the thousandths of a foot are possible.
For readings less than 7 ft the target is attached on the bottom section of the rod and adjust by signals from level operator until the target is inline with the level's horizontal cross hair.