relative thereto the distal linkage 34 can include a pin member that slides within a slot 22 c formed in the anvil and that allows pivotal movement of the distal linkage 34 relative to the anvil 22 as indicated above the support 30 can also include a middle linkage 36 as shown in fig2 c and 2d the middle linkage 36 is pivotally coupled at a first end 36 a to the distal end 32 b of the proximal linkage 32 and to the proximal end 34 a of the distal linkage 34 such that all three links 32 34 36 are pivotally coupled to one another at a mid portion of the support 30 the second end 36 b of the middle linkage 36 is pivotally coupled to the elongate shaft 12 at a fixed pivot point 36 c such that the middle linkage 36 cannot slide relative to the elongate shaft 12 in use the connection between linkages 32 34 36 allow the support 30 to move between a proximal collapsed position in which the anvil 22 can pivot relative to the cartridge arm 24 and a distal extended position in which the support 30 is effective to limit or prevent deflection of the anvil 22 when one or more staples are driven from the cartridge arm 24 and deformed against the anvil 22 the proximal collapsed position in.