An improved highback adjustment system for a splitboard boot binding. A captive strut is mounted on the spine of the highback, the strut having a forward lean adjustor block such that rotation or sliding of the block lengthens or shortens the strut. The combination provides a broadly adjustable range of forward lean bias in small increments and the block is readily disengaged and stowed on the highback when not needed. Advantageously, the mechanism that can be operated and adjusted without tools, even with gloved hands, a significant benefit in winter conditions, and does not jam with snow. Methods of use of the improved forward lean adjustor and highback are also disclosed.