Homes are filled with the ghosts of past residents. Children grow up and move on, but the rough pencil marks in doorways that marked their height on each birthday remain.

When the family moves away and the movers pack up the last box of belongings, those informal growth charts get left behind. But what if empty nesters could take those marks with them, even hang them on their new walls as a treasured memento?

At the Skowhegan Wooden Rule Co., Steve Meisner and his son make Timeline Growth Rules that are meant to become family heirlooms. The company’s main business is building cedar hot tubs, but in 1999 the Meisners purchased a rule-making company that makes old-fashioned wooden rules, the sort that are still used by fabric businesses, glass cutters and steel mills.

The Timeline Growth Rule, however, is now their biggest seller in the rule market. Everyone charts their child’s growth, Meisner said, “and nobody thinks about taking it with them. People used to be in the same house forever. I’m 68, and we grew up in the same house and the family was always there, but people now are much more mobile.”

The growth ruler is made of solid Maine sugar maple and is 6 feet, 6 inches long. The numerals are not superficially printed on the ruler.

“It’s made the way rules were made right after the Civil War,” Meisner said. “It’s an engraving and filling process, and one of them looks 100 years old the day that we make it.” Each end is fitted with a solid brass end cap.

“Basically, it’s a memo pad,” Meisner said. “You can put a child’s entire history on the rule. There are graduations on one side; on the other side, if you flip it over, it says milestones at the top, and you just start taking notes.”

Timeline Growth Rules cost $79, shipping included. Order online at skowheganwoodenrule.com.