A portable ladder module is provided, comprising a primary support member having a first step; a secondary support member having a second step, wherein the secondary support member is slidable relative to the primary support member. A lock is operatively disposed between the primary support member and the secondary support member for selectively locking the position of the secondary support member relative to the primary support member in an extended position and a retracted position. A strap having a quick-release buckle is secured to the primary support member for holding the ladder module to a tree, and a pair of rigid tubing members on each of the primary support member and the secondary support member are present for stabilizing the ladder module against the tree. Preferably, a third step is provided on either the primary or the secondary support member, depending upon the nature of the sliding relationship between the primary and secondary support members. Optionally, the first, second and third steps include retaining tabs, as well as upper and lower non-slip surfaces to prevent a climber's shoes from slipping off the ladder module.