These are Douglas Fir Mine Guides 5-1/2″ x 7-1/2″ x 18′ long that we are making for a customer with a gold mine over-seas. These pieces are for the structure of the elevator shaft; as the elevator goes further down into the mine they add the new mine guides to the structure and the elevator can continue downwards. These are graded under a specific grade rule NLGA Para 189b Select Mine Guides for structural strength. Douglas Fir is the best species for this as it has a very high size to ratio strength.