the gear rests on the main shaft with a bearing between the shaft and gear the gear is meshed with a gear on the output shaft.
the hub slides on the main shaft, there are teeth that mate with the main shaft and are kept in by snap rings.
the blocker ring is between the hub and gear…on T56’s at least, the blocker ring rests on the gear with a friction surface (much like auto clutch dics i believe, but dont quote me on that ive never built an auto so idk really) and is a cone shape. when you shift the output shaft is connected to the input shaft because the gear is now spinning with the input shaft because of the hub. so the gear sits idle untill it mates with the hub which causes it to spin.
i could probably draw it better than i can explain it, hopefully this is somewhat a productive post and not just rambling…