An assembly tool for engaging an end effector assembly with a shaft of a surgical instrument includes first and second components configured to releasably engage one another to form a body having a lumen extending therethrough. One of the components configured for receipt of at least a portion of an end effector assembly of a surgical instrument. A block is operably coupled to the first or second component and is movable relative thereto between a blocking position, wherein the block inhibits engagement of a shaft of the surgical instrument with the end effector assembly, and an unblocking position, wherein the block is displaced to permit engagement of the shaft of the surgical instrument with the end effector assembly. The block is configured to move from the blocking position to the unblocking position upon insertion of the shaft of the surgical instrument into the body in proper orientation relative thereto.
