3On the left you can see the modern bunk, which is intended for contemporary trailers and campers.

4On the right is the more rustic style, for log cabins and gypsy caravans etc.

The double is not shown.

Default height is just a little lower than normal bed height (so you can use it with my embedded booth seat places).  There are menu options to position the bed on the floor, above adult head height  and about mid way between seat height and head height, giving 3 usable bunks.  Players with Apartment Life can adjust the height also with the [ and ] keys.

Menu option allows you to choose whether or not to allow intersection of other objects and sims.  Eg a low bunk would look stupid having a sim walk through it, but a high one should allow a sim to walk under it.

For players without AL and trying to adjust height in build mode, there is a little Autoplacement Indicator.  If you put that on your lot (I think it's in Bedroom and Misc/Misc for $1 - looks like a CD-Rom) then every time you grab the bed it will change height.  At top height it will also turn itself intersectable so sims can walk under it.  NB for some reason when you delete this autoplacement indicator it goes on working until you exit and re-enter the lot.  Just so it doesn't take you by surprise

ijAutoplacerIndicator.zip (no overrides)

I suggest you also use "Use Inaccessible Beds" hack at  http://www.simlogical.com/sl/Sims2Pages/Sims2_Sleeping.htm if you have Apartment Life, to help your sims get into the double bed if it is placed against a wall.