by KoE » Tue Apr 13, 2010 9:23 pm
You need to have two cornerposts exactly two tiles away from each other, then you can right click one of them and you get a 'Make gate to (direction)' option. This is how it works for all 'wall' type objects.
However, because the devs absolutely abhor uniformity amongst mechanics, chickens are not persistent objects and this won't work unless you physically remain near the temporary 'coop'. You would probably save more trouble by building a cupboard (if you have a house, anyway) and temporarily stuffing the chickens inside it while you put up the coop. They'll die eventually, but it takes a couple of real-life days if memory serves.