World War I-themed play Through These Lines is on a regional tour across NSW and Fort Scratchley will serve as the backdrop for the first stop of the nine-town run.

Through These Lines is an Australian play by Sydney writer Cheryl Ward, based on the letters and diaries of Australian army nurses in WWI.

It follows the four-year journey of Sister Florence Whiting, from her departure on the troopship Kyarra to tours of duty in the Dardanelles, Lemnos, Egypt, France and the casualty clearing stations of the Western Front.

Through These Lines will be performed at historically significant sites, including Trial Bay Gaol in South West Rocks, the Lithgow Small Arms Factory Museum and the Bunker Cartoon Gallery in Coffs Harbour.

Kate Skinner, who plays the lead character of Sister Florence Whiting, said each of the locations presented a new challenge for the actors.

"Sometimes we will have the audience on both sides, other times it will virtually be set up like a theatre in the round," she said.

Skinner said the Fort Scratchley tunnels could prove to be a nightmare for some of the men, with a few of them towering above the rest of the cast.

With the actors now in the final few weeks of rehearsal, the actors are being set new challenges every day with the director switching up locations.

For instance, the actors would perform the first scene like they would in the Fort Scratchley tunnels, then the next like they would perform it like they would in the Trial Bay Gaol.

"Right when we feel comfortable with a scene it changes - but that's all part of live theatre and performing in real time," Skinner said.

Despite its challenges, Skinner said she was thrilled to be part of the production.

"This story is based on letters written by real people," Skinner said.

"I feel somewhat pressured to tell the story right - often the female voice is overlooked so these opportunities can be rare."

■ Through These Lines will be on at Fort Scratchley from July 24 until August 5. Go to civictheatrenewcastlebookings.com.au for tickets.