Daniël, founder of Bedbinder Deluxe
What is the best gap filler for a split king adjustable bed? The one that holds when you sit up
On a split king adjustable bed, don't just fill the gap: hold both mattresses together. The Bedbinder Deluxe split king bed bridge does that with three straps underneath, so you can still raise the head.
- Close the gapboth Twin XL mattresses stay together
- Keep the adjustabilityyou can still raise your head end
- Nothing to push backno wedge to put back every morning
- 7-year buckle warrantyif a buckle breaks, you get a new Bedbinder
A gap filler hides the gap. The Bedbinder stops it from opening.
Slide across and compare. On the left, a foam wedge sits in the gap, but the two mattresses are still loose. On the right, the Bedbinder pulls them against each other, so there is nothing left to fill.
Tried foam before? So did she.
“… I tried several things, foam wedges that sink down and straps that come loose, but nothing really worked. … The mattresses are locked tight together, you no longer feel the seam and the bed feels like one piece. …”
Translated from Dutch · Show original
“… Ik heb verschillende dingen geprobeerd, foam wiggen die wegzakken en spanbanden die loslaten, maar niets werkte echt. … De matrassen zitten muurvast aan elkaar, je voelt de naad niet meer en het bed ligt als één geheel. …”Best split king gap filler for an adjustable bed: three types compared
Most fixes for a split king gap are one of three types: they fill the gap, cover the seam, or hold the mattresses together. On a flat bed they look alike, but raise one side and you see the difference.
Fills the gap
Foam wedge
Covers the seam
Topper over both
Holds the mattresses
Bedbinder Deluxe
Our take: on a split king where only the head end adjusts, hold the mattresses together instead of filling the gap. But if the head and the foot both move, we don't recommend the Bedbinder. We say so plainly under when the Bedbinder isn't the pick.
Why the gap comes back every time one side moves
Is the wedge halfway out of the gap again, after one of you sat up to read?
Your split king isn't broken. It's two Twin XL mattresses on two bases, and nothing holds them together. So every time one side moves, they drift a little further apart.
So the mattresses stay together, and you can still raise your head end.
From gap filler to Bedbinder in 60 seconds
Lower both sides flat first. No tools needed, and it takes 60 seconds. Once the straps are on at light tension, the mattresses stay together.
Filler out, mattresses together
Take out the wedge and push the two Twin XL mattresses as close together as you can. Lay the Bedbinder across the bed on the flat part between the hinge points: straps on one side, buckles on the other.
Straps underneath
Lift the side of each mattress a little and pull the straps under it, over to the buckle side.
Buckle up and tuck under
Thread the straps through the buckles and pull them snug. Not too tight: once the mattresses can't move apart, it's right. Then tuck the buckles under the mattress.
The Bedbinder Deluxe is a split king bed bridge: not a foam gap filler, but a wide band with three straps that holds both mattresses together. That's why people also call it a mattress connector.
How the Bedbinder goes across the bed and the straps go underneath
Will it fit my split king?
And then?
Then make it one bed: a mattress pad and one King fitted sheet over both, or a split-head King sheet if the heads move on their own. In the first week the band can settle a little, so check it once and tighten the straps a touch if needed.
Which gap filler for your split king?
Works on a split king adjustable base if only the head adjusts. If the head and the foot both adjust, we don't recommend the Bedbinder. Pick your base below.
Only the head moves: the Bedbinder
Place the Bedbinder a little lower than usual, on the flat part between the hinge points, because it doesn't belong over a hinge. So you can still raise your head end, while the mattresses stay together.
Head and foot both move: not the Bedbinder
If the head and the foot of each side both adjust, we don't recommend the Bedbinder. A topper can soften the seam, but it doesn't hold the mattresses. So ask Daniël: he'll gladly think along about another way, free of charge.
Sleep Number, Tempur-Pedic and other brands
The same rule applies as on any adjustable base: yes if only the head moves, not recommended if the head and the foot both move. These mattresses often have soft sides, so use light tension. The Bedbinder isn't attached to the frame or the base, but for their warranty terms, check with the brand.
Flat base or box spring: the Bedbinder too
Even without moving parts, two Twin XL mattresses slide apart when you both toss and turn, and a wedge slides right along with them. The Bedbinder holds them together, without attaching anything to the base.
What customers say on Google
People who had the gap for years, in their own words.
Does it stop the sliding?
“Perfect for sliding matrasses! Now we alltogether sleep tight”
Skeptical? So was he.
“I was skeptical at first, but Bedbinder Deluxe hit the mark right away. No gap, everything stays tight. …”
Translated from Dutch · Show original
“Ik was eerst sceptisch, maar Bedbinder Deluxe was meteen raak. Geen gap, alles blijft strak. …”Will I feel or see it?
“… No more hassle with shifting mattresses or that annoying gap in the middle. It is easy to install and stays invisible under the sheet. …”
Translated from Dutch · Show original
“… Geen gedoe meer met verschuivende matrassen of die vervelende spleet in het midden. Het is makkelijk te installeren en blijft onzichtbaar onder het laken. …”When the Bedbinder isn't the pick
A comparison is only fair if it also says when you don't need the Bedbinder. So here they are.
And on Trustpilot
Customers who wanted the middle of the bed back, on Trustpilot.
4.3Excellent on Trustpilot
Can we lie in the middle again?
“Finally no more gap between our mattresses. Especially if you like to lie a bit more in the middle of the bed, that was pretty annoying for us. Since we started using the Bedbinder DeLuxe, the mattresses stay together well.”
Translated from Dutch · Show original
“Eindelijk geen gleuf meer tussen onze matrassen! Vooral als je graag wat meer in het midden van het bed ligt, was dat bij ons behoorlijk irritant. Sinds we de Bedbinder DeLuxe gebruiken blijven de matrassen goed bij elkaar.”Does it do what it says?
“Does exactly what they say, turns two separate beds into one bed, really a great buy for us”
Translated from Dutch · Show original
“Doet precies wat ze zeggen, maakt van twee losse bedden een bed echt een super koop voor ons”Does it last?
“I have been using it for 4 years and really recommend it. I was always wrestling with that gap, sliding again and a gap again. This solves it completely”
Translated from Dutch · Show original
“Ik gebruik hem al 4 jaar en is echt een aanrader. Ik lag altijd te stoeien met dat gat en weer schuiven en weer een gat. Dit lost het helemaal op”More questions about gap fillers for a split king adjustable bed
Is your question not here? Ask Daniël. He answers it himself, within one business day.
What is the best gap filler for a split king bed?
No single gap filler is best for every split king, because it depends on your base. If only the head adjusts, skip the filler and hold both Twin XL mattresses together, like the Bedbinder does with three straps underneath. If the head and the foot both adjust, we don't recommend the Bedbinder.
Does a foam wedge work on a split king adjustable bed?
No, not for long. A wedge only fills the gap and isn't attached to anything, so when one side tilts, it tilts too and works loose. The mattresses underneath still drift apart.
Can a mattress topper fix the gap on a split king?
No. A topper covers the seam, so you feel it less, but it doesn't hold the two mattresses together. If they drift apart underneath, the gap comes back.
Does the Bedbinder work if the head and the foot both adjust?
No. If the head and the foot of each side both move, we don't recommend it. It works when only the head moves: place it a little lower, on the flat part between the hinge points.
Does it work on a Sleep Number or Tempur-Pedic split king?
Yes, if only the head moves, at light tension because the sides are soft. If the head and the foot both move, we don't recommend it. For the warranty of your bed, check with the brand.
Will I feel the Bedbinder in the middle?
No. It is 0.04 inch (0.1 cm) thin and lies flat under your mattress pad and fitted sheet, so you don't feel the band itself.
Do I need one sheet over both mattresses?
Yes. Once the mattresses are held together, two separate fitted sheets no longer fit. Use one King fitted sheet, or a split-head King sheet if the heads move on their own.
Can I try it on my own bed first?
Yes. You get 90 nights to try it when you order on bedbinderdeluxe.com.
Why I hold mattresses together instead of filling the gap
It's 2007, and I'm in a hotel at SnowWorld in Landgraaf, on two mattresses that keep drifting apart. The next morning, in the shower, I know it: those mattresses have to be tied together. Back home the bed stores offer me non-slip pads and foam bridges, but nothing that really holds two mattresses together. So I make it myself, and I still answer customer questions myself.
Daniël, founder of Bedbinder Deluxe
Updated October 31, 2026
Sit up in bed tonight. The gap stays shut.
For a split king where only the head adjusts, one Bedbinder holds both Twin XL mattresses together. It goes on in 60 seconds, and when you order on bedbinderdeluxe.com you get 90 nights to try it at home.
- 90-night trial
- 7-year buckle warranty
- Free shipping
- Ships right away
Read more about split kings
Split king bed bridge: close the gap, keep the adjustability
How the Bedbinder holds a split king together, which beds it fits and what it costs.
Read more
Mattress sliding on an adjustable bed
Why the two sides drift apart, and how to keep them in place.
Read moreBest bed bridge: all four types side by side
Foam bridges, kits, toppers and straps, for every kind of bed.
Read more