This is the HO Scale Common Pile Trestle - Build Straight or Curved - Kit from Blair Line.
Common wood pile (with round piers driven into the ground on the prototype) trestle found on nearly every railroad in North America. May be built straight or curved. Most parts are pre-cut, and kit includes full-size template and curve templates to aid in assembly. Includes a section of Micro-Engineering's Bridge Flex Trak.