The pointy bits of wood that look like giant saw teeth from the previous pics (remember those?) are screwed on to the posts and short lengths of deck are screwed on top to make steps. (hence the dalek pun. Don't get it? Never mind)
You can buy the top and bottom rails and uprights for between the posts for the classy look and to stop your mates falling off it when they've been supping the sauce!
They are dead easy to screw on especially when you've done such a good job of concreting in the posts.