A surgical stapler, comprising: a handle (102, 104); a staple cartridge channel configured to receive a staple cartridge; a distally moveable pusher bar assembly configured to advance a staple sled assembly within the staple cartridge to deploy staples from the staple cartridge; and an anvil assembly, comprising: an anvil channel; an anvil plate comprising a positioning surface and a staple forming surface, wherein said anvil plate is movably retained to said anvil channel, one of said anvil channel and said anvil plate including at least one retention pin extending therefrom, the other of said anvil channel and said anvil plate including at least one retention slot, and wherein said retention pin is positioned to slide within said retention slot in a direction transverse to the axis of the retention pin such that said anvil plate can slide relative to said anvil channel along a predetermined path; and an adjustment member movably positionable intermediate said anvil channel and said anvil plate, wherein said adjustment member has a first portion having a first thickness and a second portion having a second thickness, wherein said second thickness is different than said first thickness, and wherein said adjustment member is movable between a first position and a second position to selectively position one of said first portion and said second portion intermediate said anvil channel and said positioning surface of said anvil plate such that the anvil plate slides along said predetermined path to provide different staple forming heights. a handle (102, 104); a staple cartridge channel configured to receive a staple cartridge; a distally moveable pusher bar assembly configured to advance a staple sled assembly within the staple cartridge to deploy staples from the staple cartridge; and an anvil assembly, comprising: an anvil channel; an anvil plate comprising a positioning surface and a staple forming surface, wherein said anvil plate is movably retained to said anvil channel, one of said anvil channel and said anvil plate including at least one retention pin extending therefrom, the other of said anvil channel and said anvil plate including at least one retention slot, and wherein said retention pin is positioned to slide within said retention slot in a direction transverse to the axis of the retention pin such that said anvil plate can slide relative to said anvil channel along a predetermined path; and an adjustment member movably positionable intermediate said anvil channel and said anvil plate, wherein said adjustment member has a first portion having a first thickness and a second portion having a second thickness, wherein said second thickness is different than said first thickness, and wherein said adjustment member is movable between a first position and a second position to selectively position one of said first portion and said second portion intermediate said anvil channel and said positioning surface of said anvil plate such that the anvil plate slides along said predetermined path to provide different staple forming heights. an anvil channel; an anvil plate comprising a positioning surface and a staple forming surface, wherein said anvil plate is movably retained to said anvil channel, one of said anvil channel and said anvil plate including at least one retention pin extending therefrom, the other of said anvil channel and said anvil plate including at least one retention slot, and wherein said retention pin is positioned to slide within said retention slot in a direction transverse to the axis of the retention pin such that said anvil plate can slide relative to said anvil channel along a predetermined path; and an adjustment member movably positionable intermediate said anvil channel and said anvil plate, wherein said adjustment member has a first portion having a first thickness and a second portion having a second thickness, wherein said second thickness is different than said first thickness, and wherein said adjustment member is movable between a first position and a second position to selectively position one of said first portion and said second portion intermediate said anvil channel and said positioning surface of said anvil plate such that the anvil plate slides along said predetermined path to provide different staple forming heights.