In a room down the hall from the home team’s clubhouse at Nationals Park, tucked behind another room adjacent to Nationals clubhouse and equipment manager Mike Wallace’s office, are scores of bats, helmets and red bins filled with other baseball necessities. There’s also a wooden school desk with a browned cow femur mounted on top of it. The bone is at least 38 years old. How do we know? Well, because 38 years ago, when Wallace was working for the Royals, he walked into a Kansas City butcher shop and bought it. He doesn’t remember how much it cost, only that it wasn’t much. The butcher cleaned it for him, and then he bolted it onto a desk he found so Royals players could “bone” their ash bats.

“They’ve been doing that, boning ash bats, forever,” Wallace, known as “Wally” throughout baseball, said. “Guys used to use sink counters or coke bottles. And some of the old places you hear about they’d use old bones.”

So, what is bat boning? It’s the old — and legal — practice of rubbing the barrel of a bat against a dried-up bone to compress it. The thinking is the process makes the bat denser so it doesn’t fray as quickly and lasts longer. Sometimes major league clubhouses have actual bones for players, other times players use sinks or toilets, which are standard in the minor leagues.

“If you go up through the ranks, it becomes more sophisticated,” Nationals left fielder Jayson Werth said. “More sophisticated ways of boning your bat.”

Wallace has taken that cow femur on each of his stops since buying it in 1979, from Kansas City to Miami to Montreal to the District. But players don’t use it nearly as often as they did a couple decades ago because bat boning isn’t nearly as prevalent now that players rarely use ash. Most players began using maple bats by the end of the 1990s – Barry Bonds was one of the first to make the switch — and it’s now nearly the universal choice. Maple is a harder, denser wood, whereas ash is lighter and has some flex, but splinters.

“The thing with ash is when you square it up on the sweet spot, it has a little give to it,” said Nationals hitting coach Rick Schu, who used ash during his career and boned his bat in Philadelphia. “No better feeling. You got that whip. When you catch a barrel on the sweet spot, it’s a good feeling.”

Fraying isn’t a problem with maple, and bat companies usually compress the bats before shipping them to players nowadays anyway.

“All these companies come with these proprietary finishes,” Werth said. “They don’t really tell you what they do with it. They claim that their bats are harder than anybody’s.”

Wallace said Stephen Drew and Ryan Zimmerman are the only Nationals players that still use ash bats. Zimmerman said he has switched between maple and ash throughout his career and hasn’t used ash in a couple seasons, but he bones his ash bats when he uses them.

“Maple is so much more consistent,” Zimmerman said. “When you’re younger, it’s easier to get a good maple bat than it is to get a good ash bat. So if you’re younger and haven’t done as much in the big leagues, you didn’t really get the good bats.”

The 38-year-old Werth said he used ash for his first two or three years as a professional in the late 1990s before switching to maple. He said he boned his bats about a dozen times, but isn’t convinced the practice made a difference and wondered if someone could do a study on it.

“It didn’t help me hit the ball,” Werth said. “If I hit the ball on the sweet spot, even on an unboned bat, I’m going to hit it hard.”

Adam Lind first heard about bat boning from a minor leaguer when he was in high school in Indiana. He did it to his bats, but admitted he didn’t know the reason behind it.

“I don’t really know what it does,” the 33-year-old Lind said. “Is it illegal?”

When told that Wallace had a bone for players to use, Lind said he wasn’t surprised because it’s standard for older clubbies. He said the Mariners had one last season, but it was used for something else.

“I know the bone in Seattle last year somebody got mad and it disintegrated,” Lind said. “Yeah, somebody beat the [crap] out of it after an at-bat.”

Wallace’s cow femur is still around, in that back room waiting to be used.

“I think you’re better off finding a bat that has hits in it,” Werth said. “And if it doesn’t have hits in it, get rid of it. That’s my philosophy. But what do I know?”

Hat tip to FanGraphs’ Effectively Wild podcast for bringing up bat boning and Wallace’s cow femur on a recent episode.