Im very surprised no one has mentioned this before, for me its been common practice for decades.

Clear Packing Tape.
The stuff with a matt finish and about 50mm wide is the best. You can buy a roll of it very cheeply from any stationers or post office.

I lay out the map down and place weights on the edges to get it flat and straight. I cut a piece of tape about 20mm longer than the map and stick it down, starting from the top, going over the edges about 10mm.
I work down the map, overlapping the tape about 5mm(Ive found this is most important) and then go over the edge at the bottom too.
I turn the map over and do the other side.
I cut all the edges straight then if Im feeling really nice I fold lengths of tape over the edges to totally stop water seeping in.
The maps are a little thicker when they are done, but this depends greatly on the tape you buy.
Even the very thin/cheap tape works well, its just a little harder to lay down without wrinkles/bubbles. To fix the wrinkles/bubbles I ***** them with a pin and squeeze the air out that way.
The maps can be folded and unfolded endlessly without damage.
I found a marker somewhere in Estonia that wrote easily on the tape and I was able to wipe it clean again with window cleaning liquid... I lost the marker somewhere in Taiwan and cant remember its name, sorry.

Ive done this to all my maps. As I dont have a GPS, maps are quite important.

N

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