Selective binding, directed transport, and a diffusion barrier conspire to achieve protein sorting between distinct compartments of photoreceptor cells. Top: Acylated probes are enriched in the OS through directed transport supported by hindered diffusion in the connecting cilium. Their weak membrane binding enables them to diffuse rapidly throughout the OS. Bottom: Enrichment of prenylated, charged probes in the synaptic region is consistent with strong membrane binding and simple diffusive transport. Illustration produced using SMART (Servier Medical Art; https://smart.servier.com) in accordance with a Creative Commons Attribution 3.0 Unported License (https://creativecommons.org/licenses/by/3.0/).