There is always room top/bottom to accommodate blankets and such. That should hold true for just about any head board/ rails/footboard style bed. It does sound like you have more than average. A standard kind is wider and shorter than a CA king so it isnt to accommodate the size difference from one king to another as many beds have the option of moving the rails from king to CA king. a CA king is the longest mattress you can buy that is considered a standard size. Since you have had the bed so long I doubt there is anything you can do to remedy that situation.

This thread discusses your issue and list a manufacturer for replacement rails. I hope it helps you.

https://www.houzz.com/discussions/wood-bedding-frame-is-longer-than-my-mattress-dsvw-vd~2367777

On all the king beds I have had they usually have two slots for the rails. One narrower width for CA King and one wider width for king so that your box springs can fit snugly width wise. It sounds like she has extra long rails. I wonder if this manufacturers standard king rails would accommodate her CA king bed. Maybe their king rails are also longer than average ? Since they have owned it for so long the odds of there being a remedy are slim.

See above link. It discusses how some manufacturers do the extra wide gap on purpose and that by checking the mattress length, the homeowner can order replacement rails the length they prefer for a much smaller reasonable gap.

Have ONE large piece of high density foam ( 76 x whatever and whatever )cut to width of mattress and depth of gap at HEAD of bed, and have it covered in a cheap Sunbrella white. Then stop agonizing. Put it back there, attach with Velcro strapping to mattress sides. Or mount it to the wall in the exact spots behind the headboard, and invisible.

Given it is a sleigh bed, the first option makes more sense. Or fill the bottom TIGHTLY in the same way.

Thank you all! This is not the first CA king bed I've had, but def. the first one with this wide gap on both ends of the bed.

Seems like we may have to find a solution similar to what Jan suggested and call it a day. Either that or I can have my hubby sleep horizontally to fill the gap up top! ;)

Mattresses don't ""slide" , Really, what difference does it make if the gap is at the foot of the bed. ? Just shove the box spring and the mattress to the headboard snugly, and cease to worry about the foot of the bed and footboard.

If there is a large gap from the BOTTOM OF THE HEADBOARD to the mattress top? ? That is bed design flaw, really. Consider a deeper or extra box spring for a boost up. Post a photo of this with a stripped down bed : )

Jan - You crack me up. :). We can shove the box spring and the mattress to the headboard, and have just one big gap at the end of the bed, however we have a small pet that will most likely fall through it if we do.

Yes, there is a large gap from the bottom of both the headboard and the footboard to the mattress top. Our mattress sits pretty high up as is - top of mattress is about 33" from floor (and I'm a short girl - 5'2"). If we get any more boosts up, I will need a ladder to get into bed! :)