Methods and apparatus for ensuring the proper handling of reticles in the manufacturing of microdevices are disclosed. The methods and apparatus employ one or more reticle stop blocks fixed to a reticle handling arm. The one or more reticle stop blocks are designed and arranged to engage an edge of the reticle in order to place the reticle in a desired position on the reticle handling arm should the reticle be improperly arranged in a cassette in which the reticle is stored. By ensuring proper placement of the reticle on the reticle handling arm when the reticle is removed from the cassette, the likelihood of a subsequent fault in handling the reticle is greatly reduced.