Question about headboards!

[Abcd3]

Please forgive my ignorance, but I can’t remember - does the bottom of a headboard line up with the top of the bed or the top of the mattress? I need to know in order to know what height of headboard to buy!

I've always lined mine up with the top of the mattress. That's because the mattress is so deep the headboard would practically disappear behind it. That said, I don't know if it's correct or not.

I've always lined ours up with the top of the mattress too.

I think it's supposed to be the top of the mattress which is why some headboard have those slatty legs and you slot them onto the bolts on the head end of the bed and tighten them to the level required

Thank you!