What I meant to say was that they are so difficult to open I would have to break them to remove them. Not that they are breaking easily. I would rather not clip them if there is a better way to remove them, thus leaving me with some spares after I use the new ones I bought for the new sail. The old clips have only been used one season.
While it may not be the correct way what's worked for me is just a wide bladed flat screwdriver in the end gap and twist. I've got 30 year old clips that still work great and I've had one year old ones that wouldn't stay closed. Sooner or later most all of them harden up from UV and Pollution and snap when trying to open them.
The "Sunfish Bible" gives a rigging outline on what clips to replace with line. But I still have boughten spares over the years.
There is actually a tool made to "undo" these nylon sail clips, but in the absence of that tool, I have found that using two, large flat screwdrivers will do the job. Put the blades side by side and insert at the open end of the clip and twist gently and the clip will open without damaging the clip, the sail cloth or the brass grommet.
In the same respect, what is the best way to close the clips? I use a pair of channel locks which requires the teeth to be on the sail material so if you slip, you could damage the sail. Any better ideas?
I went "hitech" and bought a pair of welding Vise Grips. They have a hugh throat that fits over the spar. I added a pair of slip on plastic jaws to protect everything. I set it once and I never have to worry about "crushing" a clip.
I made a simple sail clip remover out of a .99 cent hole punch from Staples. A hack saw or Dremel tool can be used to make the "hole" part into a "U" shape. Slip it over the clip,squeeze, and it pops right out.
To get them back on, try a little soap on the tip of the clip. It slides into the hole much easier.
A pair of simple wire cutters with angled edges works very well to remove sail clips. Just slip the cutters between the clip and the sail grommet and squeeze. The angled edges of the cutter pushes the clip apart. Don't squeeze so hard that you damage the post part of the clip. If you want to you can dedicate a pair of cutters to the job by grinding off the cutting edges. But it isn't necessary.