A system for forming a step protruding from a post (e.g., tree) includes a spine, a post fastener, and a step. The spine is strapped or screwed to the post via the post fastener such that the spine extends generally parallel to the post (i.e., vertically). The spine includes a length of tubing and an alignment plate. The length of tubing extends vertically along the post when installed (i.e., assembled) on the post. The alignment plate is attached to the length of tubing, typically at one or both ends of the tubing. The alignment plate extends laterally from the length of tubing to limit rotation of the tubing about a vertical axis thereof by interacting with the post when the spine is installed on the post. The step engages the spine such that the step is supported by the spine when the system is installed on the post. The step extends generally perpendicularly from the spine and post.