A cartridge assembly for use with a surgical stapling instrument is disclosed. The cartridge assembly includes a channel, a cover, a staple cartridge and a knife. The channel includes a protrusion thereon. The cover is configured for mechanical engagement with the channel and includes a blocking member and a surface defining a plane. At least a portion of the blocking member is configured to move away from the plane upon contact with the protrusion. The staple cartridge is configured for mechanical engagement with the cover. The blocking member is configured to substantially prevent distal translation of the knife after the knife has been translated proximally past a predetermined position.
