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The Humble Boltsnap

The more time you spend diving and the more kit you drop or lose then the more you find yourself appreciating the humble boltsnap.  Modern clips, lanyards and specialist clips are great but there isn’t much you can’t do with a basic bolt snap. Now not all boltsnaps are made the same and they come in a range of shapes and sizes for specific uses to the point where I have a specific draw in my tool chest at home dedicated to the boltsnaps I’ve collected over the years…

In this blog we’ll be taking a closer look at different boltsnaps and how to use them properly.

Anatomy and Benefits

A boltsnap has a hook at one end with a spring loaded gate that defaults in the closed position.  At the other end is the eye which swivels which is the fixed attachment point.  Most boltsnaps for diving are made from marine grade steel but you can find some made from brass but brass is a softer metal and can bend pretty easily so I tend to stick to steel ones with a smooth gate.

Some cheaper boltsnaps aren’t machined very well and don’t run smoothly so aren’t the easiest to open and close.  Inside is just a small spring that closes the gate but these can often be made from a cheaper metal so it’s best to wash them out thoroughly and dry after dives to prevent rust and salt build up.



Unlike carabiners and other clips boltsnaps are less likely to create a snag point. Boltsnaps are incredibly simple to use and pretty universal so you can use them even with thick chunky gloves and cold hands.

A wire gate carabiner can clip itself onto a line or snag point with an unintentional movement and can be tricky to disconnect from larger items so best avoided in the water. Boltsnaps require a specific movement to open the gate and hold it open and when clipped on it’s easy to unclip no matter the size of the line.

The size of the boltsnap denotes its use, small boltsnaps like a 64mm with a small eye are for tying onto accessories or 2nd stages because they don’t get in the way and they do the job.  For heavier items like stage cylinders you’ll want a bigger boltsnap so you can feel and control the item with one hand. A larger eye can be used as a finger hold giving you good purchase and control of the attachment point and item.



There is one downside to the humble boltsnap and it’s mainly due to improper use. Mainly seen on spools if you attach a boltsnap to a hole in a spool in a certain way it can work free by mistake but it’s easy to avoid by attaching like this.


Single Vs. Double Enders

Single enders have a swivelling eye on one side and a spring loaded gate on the other and they’re mainly for fixed attachment points on accessories or hoses and I’ll show you how to tie them on later. Double enders have a spring gate on each end and are mainly used for reels and lines where you want to temporarily attach something.



Specialist Boltsnaps

The only other design you tend to see diving is the Shackle Boltsnap which is a semi-permanent single boltsnap with a screw gate eye. These have a specific use and that’s to attach to gauges or accessories with a fixed mounting point but without a flathead screwdriver and regular maintenance they can seize up and be hard to remove especially when rust and salt builds up.  They’re great for what they’re made for but for attaching to hoses and tools most tie them on so they don’t slide around and rattle and you can cut them free in an emergency.


Attaching Boltsnaps

This may sound remedial but it will save you from losing kit and fumbling in the water…




Fitting a single to a hose you’ll need a length of line from a reel or spool, a sharp pair of scissors and a lighter or heat knife to seal the ends. For 2nd stages I use a small 60 to 75mm Boltsnap and for SPGs a larger boltsnap with an eye big enough to fit a finger through for control like a 105mm.

Depending on your training guidelines fit the boltsnap on the hose starting with a cow hitch to the eye in the middle of the line.  Then loop both ends of the line around the hose and through the eye three times and tie down between the hose and eye with an overhand knot and a square knot on the other side to fix it securely in place and melt down any extra line so it doesn’t fray. I usually fit mine about a fist away from the body of the 2nd stage or SPG so you know where it will be at all times and it doesn’t get in the way.




Spools typically arrive new out of the box wrong with just a small loop in the end of the line.  What you really want is a leader on the end of the line with a nice big loop big enough to fit the whole spool through it with some room to spare so you don’t have to struggle in the water.

With a spool you’re double ender has one job and that is to lock the line and stop it paying out, it has nothing to do with attaching the line to a dSMB or the likes.  When storing on a D-Ring you’ll want a length of line between the snap and the spool so it can’t unclip itself, don’t just clip it to one of the holes as that’s an easy way to lose your spool.

When you’re using your spool you can lock it off by clipping to one of the holes but it’s less likely to be lost while you’re using it.  You can add a twist to the line around the hook as an extra precaution but that depends on your training.


Tools like torches, cameras and knives etc. usually have an attachment point on them where you can attach a small single ender with a similar knot to the hose knot above, three loops and a couple knots to tie it off. 

For larger items like cylinders use a cam band or clamp band along with a large eyed single boltsnap so you can control it better in the water but there are plenty of kits out there so you don’t have to assemble yourself.


Bottom Line: What Do I Need?

For your Regs you’ll want one large eyed single for your SPG and one small single for any 2nd stage you want to clip to a D-Ring.

For a stage cylinder you’ll want a large eyed single at the top and the bottom of each cylinder.

For each tool I’d use a small single unless you dive with particularly chunky gloves then it’s up to you on size.

Spools you’ll want a good sized double ender, I usually go for a 90 or larger with a chunky trigger on the gate so it’s easy to use and I always keep a spare on me just encase…