Introduction: Three Beds in the Space of One!! a Brilliant Way to Save Space
Save space by using this hack. It's simple and easy. Instead off having three beds next to each other or having a bunk bed with another bed taking up valuable space, you should use this idea.
Step 1: The Bunk Bed
Make sure to get the perfect bunk bed. The bottom bunk should have a little more then a foot gap under the bed.
Step 2: The Mattress
Get any kind of mattress as long as it is about 6 inches tall and can fit under the bunk bed. Tuck mattress under bunk bed during the day and pull out for the night.

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Comments
Tip 5 years ago on Step 2
Things like these exist, they're called trundle beds and are commonplace in kids' bedrooms, usually for things like sleepovers. You can buy them at most furniture stores.
That being said, this is a nice cost-saving way of doing it. If you wanted, though, you could build a rudimentary bed frame with some scrap wood, drawer rails, and maybe some small wheels, for ease of use.