An insertion tool for positioning intervertebral spacers into disc spaces. The insertion tool has a proximal end and a distal end, a T-handle secured to the proximal end and a pair of alignment rails extending to the distal end. The insertion tool includes a handle secured to the proximal end of the guide rails, and a shaft that extends through the handle, whereby the shaft has a threaded portion that extends to the T-handle. The insertion tool also includes a blocker that is secured to the distal end of the shaft. The blocker includes stop arms that guide the blocker through the guide rails and toward the distal end of the shaft. The blocker may be provided in a plurality of different sizes corresponding to the sizes of the implants to be inserted into a disc space. A lock is provided for locking the implant to the shaft.