by Danno » Tue Jan 25, 2011 9:10 am
Indeed, sealing a cornerpost makes it so you can't build from it anymore. It's particularly important you seal the cornerposts at your gate so that someone doesn't simply extend it from your gate, go in front of your gate, and connect to the other cornerpost, effectively trapping you within your own home.
I'm not sure if you become unable to create a gate if you seal the cornerposts first since I've never tried it before... so build your gate before sealing them to be safe.
You don't have to worry about this with roundpole fences since they're laughable at best and don't have a sealing option. To seal a palisade cornerpost, right-click the cornerpost and choose the "Seal" option. I assume it's the same for brickwalls, though I can't say that from experience.
RIP