Although she never met either man and doesn't know anything about their history, Derr does know they signed their names to a wall under the sanctuary's roof, probably in January, 1888.
"I made the suggestion that we sign the slates to help offset the cost of the work," she said.
Members of the congregation, and the community, could sign a slate for $50. They could write their names, their families' names, or a favorite Bible verse. They signed the smooth side of the slate, which will be placed next to the roof's wood sheathing. That way, the signed side will be protected from the weather.
Derr set up tables for the slate signing and provided a selection of oil-based paint markers to help assure the writing will survive.
This is not the first time congregation members signed a work in progress.
"When the Family Life Center was being built, we all signed the concrete floor before it was covered," she said.
The members had two opportunities to sign the slates - after the two services on Sunday, June 25, and Sunday, July 2.
Only half of the sanctuary roof will be covered in new slate. It will be put on the north side of the church, facing the Family Life Center.
The south side, which faces the parsonage, will use good pieces of Peach Bottom slate salvaged from the entire roof. The parsonage is also roofed with Peach Bottom slate.
Good Peach Bottom slate that's not needed for the roof may be saved for future repairs or used for craft purposes, said trustee Larry Myers.
"If we have enough, we may sell some," he said.
The old cut nails will also be saved. If any inscriptions are uncovered during the work, they will be photographed and recorded.
All the slate will be installed using copper nails. That should prevent the most common problems with a slate roof. While the slates themselves are durable, the cut steel and iron nails rust, causing some slates to come loose or even fall off the roof.
With copper nails, the new roof may last longer than the one it's replacing.
The work is being done by Aaron Lantz Slate Roof Repair of Leola.
"He's very busy. We lined him up last year," Myers said.
After his workers remove the slate, Lantz will check the condition of the wood sheathing. If any of it is in bad condition, new pieces will be milled at a local sawmill.
The 19th century roof was installed with other renovation projects. At the same time, the church walls were 'refreshed,' which could mean that they were painted or whitewashed, Myers said. Stained glass windows were also installed at that time.
Records don't indicate if that was the first slate roof on the church.
"The sanctuary dates to just after the Revolutionary War," Myers said. "Tradition has it that the walls were put up, then the men went to war, and they finished the project after they came home."
The trustees have been considering replacing the slate roof for several years.
"There were a few leaks here and there. Nothing major, but we had seen a few slates shedding for a couple of years. We wanted to get it done before it does cause a problem," Myers said.
Weather permitting, the project should take about three weeks to complete, he said.