Just about to place an order and I noticed they have Neo magnets nice and cheap…what would be a good size that i wouldn’t need a crowbar to pry away from the grate?
10 mm thick?
20 mm?
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There are some very powerful, tiny magnets. An old Sonicare tooth brush I used to use…every time I replaced the brush, I pried off the powerful little magnets came on them. Those suckers were so powerful, you could never use them for any of your projects. In this case, size doesn’t matter. Probably most rare earth magnets will be too strong, but there lots of different manufacturers, and for our purposes, cheaper is probably better (weaker). - Rich
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What kind of grate?
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The one on which we set our items to be lazed. 
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the steal bread crumb tray
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The point, I guess, is the grate doesn’t offer a lot of area for magnets to hold on to. And if there is material (wood, leather, acrylic, etc.) between the magnet and the grate, the magnet loses holding strength as it gets farther away from the grate. I doubt you’ll need a pry bar, but I’d be careful with paper and other thin or delicate materials. Maybe a less strong magnate for them. - Rich
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You can use ring-shaped magnets and cheap drawer-pulls to make a DIY version of the magnets like this one from yellotools, used for wrapping vehicles.
Once the laser comes, I could see making use of the various tiny magnets I have laying around (totally gonna harvest from my sonicare next brush swap, great idea @chrgeup) by making them into an array with a custom-cut holder, similar to this mag by Avery, where you can see that instead of one large magnet, there are six small magnets in a circle.
The wrapping mags are rubber-coated to avoid scratching paint or vinyl. we won’t need that for everything, but non-marring finishes or coverings might be good for fragile items. The 1"-2" size is plenty large enough to gap over the honey comb
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It all depends on how powerful they are, not all magnets are created equal unfortunately.
I’d say get one of each for now, or pick some up in person when you can feel them out.
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All good suggestions…many thanks! (Might have to 3D print some handles for them, or embed them in the print.) 
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You can wrap a bit of Washi or masking tape around the little neodymium magnets, leaving a tail of tape to use as a handle.
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Like that idea…heck of a lot easier than designing a file. 
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Deal Extreme used to have a 100-pack or so of 10mm x 1mm neodymium. Those are plenty strong for holding stuff to fridges, so they’d probably do fine for honeycomb. (If not DX, doubtless someone else has them) And second or third the tape.
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Magnets are great for this, but I’m in the less-is-more camp. Our makerspace had a donation of a box of Neo magnets from dismantled hard drives. They made great work “clamps” except for one thing-- they were so strong that they damaged the grate on our laser (even with handles)!
The primary issue was underestimating the pull in that last cm before contact, and letting them bang down onto the grate. Some folks donated tissue samples to the laser gods, too. Prying them up also resulted in bent grids.
I’ll use them on my GF, but will stick (sorry) to the smallest viable magnets for the job.
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I couldn’t decide on a size, so it will have to get added on to the next order.
(I’m so pooped right now I’m getting silly. House full of workmen today.)
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Sorry for the poor pic. I bought the neodyminiumiumiumiun 
round magnets with the recessed hole in the middle. Then using the small screw, you could easily attach to a short piece of dowel. Or forge a handle that could be scewed to it ( maybe pawn shaped). The make the various sizes - mine are small but would keep paper attached w/o moving due to air assist.
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Magnets are mostly used to prevent stuff from blowing away from the air assist, right? If so, I’d also use some really small magnets. I have a collection of 1/8" diameter by 1/8" long cylindrical magnets and I think they would work pretty good if your goal is to hold down paper and other similarly-thin material. Putting tape around them so you can grab them easily is a great idea! It might make them somewhat less likely to be swallowed by kids/pets as well (swallowing magnets is very, very bad).
If you’re trying to prevent material from warping I think you’re going to have to get some larger magnets. I would think anything that could straighten a warped/warping piece of 1/8" plywood would need some fairly serious power. So much that it’s not worth trying, I would think.
Those Avery magnets look like they’re pushing it in terms of height, but I don’t remember what the typical clearance between the material and laser head is (and I’m guessing that info won’t be easy to find).
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I’d worry about rare-earth magnets being too snappy, especially snapping something against the fine-edge of the grill. Whatever happens to be between the magnet and the knife-edge of the grill, it’s potentially like slamming a chopping edge against it. You might be lazing the top of it, but the back could be marred with sharp lines you don’t want.
I’m going to finally make use of all those food delivery fridge magnets I’ve collected over the years!
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We use some flat steel blocks for this purpose. They can also hold a piece of slightly curved piece of plywood flat towards the tray. Magnets might be nice for very thin material.
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Maybe grab a rare-earth magnet and add it to a piece of metal at one end, the magnet will charge the metal and you can have the magnet at the other for different resistances?
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I use various sized ones - circles and bars. Amazon has decent deals on them. Mine are all 6mm thick or less so if the head passes over them it doesn’t whack them. I don’t laser on them but the head travel starting or stopping from the homing position might overlap a magnet.
I find that 3mm and sometimes 6mm birch ply sometimes bows a bit when stored and the neo magnets are plenty powerful enough to hold it flat.
You generally can’t pick them off with your fingers, have to slide them to the edge and then pick it off from both sides with a pinching grip. 
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