The benches, dedicated to PCs Nicola Hughes and Fiona Bone, are at Hyde police station.
Bob Graham, Illingworth Ingham’s Hyde branch manager, represented the company at the official memorial garden opening ceremony.
The company has five timber merchant branches in the area.
"The loss of these two police officers has been a terrible tragedy and we just wanted to show our support by contributing to the memorial garden which will become a very special place within the community," said company chairman Simon Gravelley.
