Boresighting of laterally separated optical systems or lines of sight may require the lateral transfer of a collimated alignment beam without the introduction of error into the look angle represented by the alignment beam. An extended retro of some sort (e.g., cube corner) is commonly used for transfer of the look angle reference. One major error source that degrades the accuracy of the extended retro is bending of the "tube" connecting the retroreflector input and output optics. Control of this bending requires that the retro-reflector be well isolated from environmental stress such as vibration or thermal gradients across the tube. Alternatively, the bend of the tube may be monitored. This paper describes some of the techniques used in the accurate lateral transfer of alignment beams. Several approaches which are functionally equivalent to an extended retroreflector are discussed. The five-surface retroreflector concept (using empty pentaprisms) is modified into an "Alignment Reference Transfer System" (ARTS), which to first order is insensitive to tube bends. Several optical configurations of the ARTS concept are shown, and the tradeoffs leading to the selection of the baseline design are described. The error sources in the baseline are pointed out. The coupling of ARTS input beam misalignment to tube bend produces an ARTS error which is the product of the two. A brief discussion of the application of the ARTS in the boresight of two apertures is also included.