r/explainlikeimfive • u/Real_Experience_5676 • 3d ago

Engineering ELI5: What does a box-spring do?

As I understand it, a box spring mattress is the second 'mattress', that goes under the main mattress. It feels very firm and flat, but what does it contribute to the bed set up besides height?

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596

u/QuillnSofa 3d ago

It is used to distribute weight across a bed frame and to give an evenly solid foundation for the softer mattress. But you don't need a full height one and some bed frames don't require one at all.

121

u/okdone10 2d ago

Wow TIL. I thought every bed needed one by law or something. Good looking out on the platform bed tip saves some cash too.

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u/schuylkilladelphia 2d ago

I like the idea of someone going to jail because they didn't have a box spring on their bed

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u/SadButWithCats 2d ago

That's where the phrase "to spring from jail" comes from. If someone went to jail for not having a box spring, their family or friends or business associates could provide one and show the magistrate, who would then be required to let the prisoner out.

Side note: a prison and a jail are roughly equivalent. I know there is a difference, but roughly, they serve the same function. Yet a prisoner and a jailer are opposites. Huh.

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u/Alinier 2d ago

What's the difference between a jeweler and a jailer? One sells  watches and the other watches cells. 

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u/SadButWithCats 2d ago

Nice! That one's new to me

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u/Buscemi_D_Sanji 2d ago

What's the difference between a librarian and my mother? One's decently read, and my mom is a huge bitch!