My bed has a nut and bolt that are recessed into a piece of wood.
The only tool I have that fits it is the tiny toy spanner that came with the bed.
The spanner does not grip the nut tightly enough to be able to turn it.
But a larger adjustable spanner/pair of grips does not fit in the hole.
How could I tighten this nut?
Update: The toy spanner did work up to a point, but now it just slips off the nut every time, as if it's too loose.
Don't underestimate what that little wrench will do, or how much torque you need to hold the bed rails together. With the lock washer, it only needs to be compressed, plus maybe another half turn at the most. The force created by the threads drawing through the nut create an incredible amount of pressure on the joining faces.
The included wrench has 2 distinct ends, one has the legs of the wrench equal lengths more or less, the other end has a shorter leg on one side. Because of the shape of the wrenches, I will assume there is little or no space to get a box end wrench around it, if there is any room behind it, then a box end wrench can be ground down enough to fit around it. A rail bolt wrench may work too, they are made to fit into even a deeper, hole. They are used for handrail assembly.
Back to the offered wrench, the one end with the short leg, in my opinion is the workhorse, the short side is always on the leading side of the turn, as in if you are turning to the right, or clockwise, the short side is on the right side. That side is shorter so it does not bottom out as quickly in the shallow hole the captured nut is in. The wrench with the equal lengths are for the nut when it is in the midway point, where the nut is being turned where the legs of the wrench will still clear the bottom of the hole. As soon as one side of the wrench touches the bottom of the drilled hole, turn it around, and use the end with the short leg to complete the turn, so to speak, then swap ends again, turn that a little, then change ends of the wrench, and repeat.
You may have tried these techniques already, but it wasn't stated in your question to what extent you tried to work with the wrench. The picture of the wrench only shows a little distortion on the short leg of the one end that would occur if the wrench is turned the wrong way. Even though there a slight distortion, having the proper orientation of the wrench to the nut, that won't matter.
You can often get a box-type ratchet wrench around those recessed nuts
These often come in sets. They are a bit pricey but have many uses. While you can also use a standard box wrench (a closed loop without the ratchet), in tight places, placing the wrench, advancing it a fraction of a turn, freeing the wrench, resetting it and turning again can get annoying.
But even a standard open end wrench (like the U shaped end of the wrench above) would give you more grip than the toy wrench provided.
Links and images are for illustration only and are not endorsements
An outside-the-box solution would be to remove a small area of wood from the railing.
We can see where the wood has already been dinged by the tool. Removing a small sloping area will make access easier in the future, and should allow a normal 4"/100 mm spanner access
Also, next you move, consider leaving the bedframe assembled, rather than going through this process every time.
I had a length of bike chain, which was too worn out to use on a bike, but still structurally strong. I cleaned it well and wrapped it around the nut. Then I clamped down on the base of the two free ends with some pliers which were outside the hole. A little tap with a hammer and cold chisel against the chain was enough to move it a few degrees, then reset.
Haven't got a photo, but imagine something vaguely like this oil filter chain-whip.
I had the same issue except there was no crescent wrench from the manufacturer at all. Needle nosed pliers worked perfectly albeit the nuts were actually not very tight to begin with.
I puzzled over this for a while then found my old and simple 1/2" ring spanner did it easily despite the tight access
Just take a pair of needlenose pliers and grab that sucker and turn. You'll only get about an 1/8 turn, but it won't take long.
My guess is the guy who told you that you are using the wrench incorrectly is probably right; have you used both sides, flipping it over and trying all the different ways? If it's catching once every 10 tries it could also be the nut is tight already and that's why the wrench is slipping off.
