>I've got a peaked roof lid on a Langstroth hive in my backyard....>
 
Hi Nick -- here's a question for you.  Why do the Australians use covers
with the same outside dimensions as the hive bodies, a couple of inches
deep, and which do not telescope down on the edges?  I've seen that they
lay a mat over the frames, and set the lid on top. It typically has
ventilation holes, too.Yet it doesn't appear that the lid is fixed or
anchored to the hive.  Don't they just blow off?  Or get knocked off?  Do
they get all clogged up with comb during a honey flow?
 
(The simple migratory (board) lids used here -by some- usually telescope a
tiny bit front and back.  This doesn't waste much space on a truck, as the
bottom boards also jut out a bit from the hive front.)
 
Also, does the equipment used in NZ differ much from that in Australia?
 
Many thanks