Loft bed construction

Hi all, I'm constructing a loft bed in the style that this chap produces... http://www.stubborn-norwegian.com/loft-beds.html
It's pretty straightforward stuff and I've reverse engineered plans from his photographs and measurements. However, I can't figure out how he's joined the headboard/footboard rails to the end posts - there's no visible join. I thought they might be screwed and plugged or doweled? In my case I've just used two 2 inch screws and brass cup washers at each join and it seems plenty strong. Anbody any ideas on how he produces a strong invisible join? I've asked him, but it appears to be a secret...
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They could be doweled, loose tenoned, or ohhhh...shiny Dominoed.
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blind dovetail with the recessed part for extra strength. Or you could buy one and have a look.
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