Auto Reflection Targets
Put autoreflection targets on the objective end of our transits and levels to provide a nice reference target to start the autocollimation process. The 186 gives you big bull's eye / paired-line target to find in that possibly-distant mirror. The 188 places the target right over the objective lens (requiring that instrument illumination be used). Center the instrument's own reticle on the image of this target as it is reflected by the mirror, and you are halfway home to setting perfectly orthogonal to the mirrored target.