Does size really matter?

I was reading a book from the libery about decorating and it said that you had to put the size on the wall before you put up paper on the wall you had sized. I can understand that you would need to know the size of the room before you got the paper but not that you had to put the size all round the room as well. Is that to make sure you remember it or is something else going on? When I asked my boyfriend about this he just shruged his shoulders and said that size did'nt matter anyway. Is that true or was he wrong again?
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Sasha snipped-for-privacy@hotmail.com (Sasha Klamp) said:

You were funny only the first time.
Two Tun
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ROTFLMAO!
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