Toggle Clasps - toggle clasps really are sort of a variant of the hook and eye, in that they are a purely mechanical clasp with a ring you hook a bar through.
In general - they consist of a ring, and a bar that is wider than the ring. To fasten these, you manipulate one end of the bar into the ring, and pull it up and through, until the other end of the bar comes up through the ring as well. Then you can let go and the bar settles back across the ring and is secure. It is surprisingly easy to do this with one hand, making these an excellent choice for a bracelet. They do need to have weight on them in order to stay closed, and I have had some problems with them spontaneously undoing themselves on necklaces. Also, the bar can interfere with the back of your neck - so I prefer them for bracelets. But that's not to say that I never use them with necklaces - but usually for bigger, heavier ones.
Because the bar needs to be the right size to slip through the ring, but not back out, these really need to be the right dimensions - and occasionally we'll get one shipped to us that was obviously not tested before they put it into production. Little gaffs like, the bar is too short, or the loop attached to the bar prevents it from sliding through the ring - those ones go in to the "defective products" bin.
They come in a huge range of styles and metals - with something to fit every budget. Some have charming little visual puns - like this heart and arrow toggle. Others make the ring so elaborate that it becomes part of your overall design.
There are some interesting variations in the category of toggles. This "Layered Leaf" clasp is still just a toggle - the smaller leaf (bar) fits through the hole in the bigger leaf (ring) and twists, to make a layered leaf look that does not read as a clasp at all, but as a design element. You can see how this floral clasp also uses form to hide function.
Our fourth category is Magnetic clasps. At it's simplest - two magnets with loops on - but lately we have seen more and more that seek to hide the magnets - making for clasps that can become invisible.
Most magnetic clasps are pretty strong, but magnets that are hard to pull apart can be very easily slid to one side. To counter accidental openings, the newer and more elaborate styles often have a post on one half of the clasp, and a hole to fit inside on the other, to prevent them from being easily disconnected. To open these - you need to slide your nail inside the opening and lift a little, and then slide apart - which is annoying if your manicure is fresh. However, for folks with arthritis, they can be a god-send, as they practically do themselves up - so long as you get the ends close enough.
You may have seen "kits" for converting hard to do up necklaces - these consist of just magnetic clasps with a ring so that you can easily attach them to existing clasps without having to modify the jewelry.
However, before modifying all your grandmother's jewelry so that she can put it on without assistance, bear in mind that you must not use magnetic clasps for folks with pacemakers. The magnet interferes with the delicate electrical signals that are communicated between the actual regulator and the pacemaker itself, and, as much as I love jewelry - I really don't think it is worth dying for. Not unless it is a really fabulous piece.
(Just kidding. A really, really fabulous piece.)
We've seen some interesting variations lately too - like these "fold over"clasps, that have a magnet in them, so that they are more secure. And these multi-strand tube clasps have a magnet in them to help hold them closed.
Magnetic clasps can be highly annoying to work with - as the magnet in them sticks to ferrous items, like - your tools! And even the stringing cable! You'll spend a lot of time unsticking them from your wire cutters, crimpers, and once assembled and stored in your jewelry box, you may pull necklace out, and find that six more came along for the ride. On the upside, you can store the stuck to your fridge or a metal filing cabinet. And they make a great clasp for making custom ID badge holders.
If your workplace requires that you wear an ID tag at all times, you may have decided that you want to hang your pass on a more attractive and personal loop than the logo-embossed ribbon that it came with. For security purposes, these need to break away should someone decide to grab your pass and make a break for it (unless you work for the CIA, in which case, I'm sure you have the training to stop that sort of thing.) If you think jewelry is not worth dying for, well, frankly, neither is your job worth being throttled by your ID badge. Just let them go and call security. (If you work around machinery - for sure you want it to break away if grabbed by a machine.)
One last caution for magnetic clasps. I don't usually use them on bracelets anymore, or if I do, I add a safety chain, a short piece of chain from one end of the bracelet to the other that the will stop the bracelet from dropping off your wrist if the clasp is accidentally opened. I find that in the winter, when you pull your big heavy coat off - it tends to drag on your wrist with enough force to open the magnetic clasp and have it come off. Because all the nerves in your arms are being stimulated by the sleeve coming off, you tend not to notice the bracelet coming off, the way you would normally notice it falling off. I can't tell you how many bracelets I have rescued from the slushy, salty boot tray by the door.
Our fifth category is Spring clasps. Generally, utilitarian and not much in the way of design choices, but absolutely a basic, stock-in-trade item. This category of clasps feature a spring loaded lever or slider that you pull back, hook into a jumpring or chain, and then release the tab. They are absolutely secure - unless you miss the ring entirely. They can be a bit awkward to do up on bracelets until you get the hang of it.
Usually, you just see the round "spring ring" clasp and the elongated or rounded "Lobster claw" clasp. They are an inexpensive and unobtrusive clasp solution.
But technically - these heart clasps are exactly the same idea.
Other oddball clasps that you might come across and want to use.
There are the "fold over" clasps - a style that has a hinge and a friction fit. You open up the clasp and put it through the attaching ring, and fold close. You should hear a little "snikt" as it snaps shut securely. To open, pull up the tab and fold out.
These Ram's Horn tension bars are very specialized, and designed to hold wide band bead work closed by sliding the bars, like a clip, into sleeves built-into the bracelet.
These snap clasps work pretty much like the button snap on your jeans -a friction fitted ball in a hole.
Barrel clasps tend to be inexpensive and are simply a screw and a threaded socket.
This combination of a box clasp and a hook and eye uses tension to keep closed, but has a post that will catch the clasp if it inadvertently comes open.
These were an interest variation - the have a ball and a slot that it fits into. Definitely does not look like a clasp once secured. I like that in a clasp. These use the same idea - they work much like the magician's traditional "linking rings" trick.
These tube clasps - that are NOT magnetic - have a spring clip on the side to provide some tension - to prevent them from accidentally sliding open. I prefer these - because of the "not sticking to my tools" thing. These are a great clasp for multi-strand bracelets.
So that's the scoop on clasps - the inside info on closures. Hope you got some "closure" from that. ;-) Now that you know what a world of choices there are out there, you don't have to use just another lobster claw!
By the way - all the image are clickable links that will take you to the product if it is in stock, and if not, to the page where you may find something you like better.