Wrist seals.
Others may have better ways, but here is how I have done it successfully several times:
Carefully peal off the old seal. Sometimes heating with a hairdryer helps.
Clean off the old glue. Believe it or not, the best way to do this is to relax, take your time and roll it off with your fingers a bit at a time. Any chemical that breaks down the glue could break down the suit material. If all the old glue doesn't come off, that's usually OK.
Sand the area with a fine grit sandpaper. Clean the area with Cotol (bought where Aquaseal is sold).
Put something into the wrist opening that is firm and sticks out about 4 inches (I use a hard foam cut to size. My LDS uses a piece of PVC pipe with a layer of neoprene over it). Pull the seal over the form and onto to wrist area exactly where you want to glue it.
Place a piece of masking tape on the drysuit around the edge of the seal where it ends on the wrist (this is so the glue won't slop over, and it'll make a nice clean line at the seal's edge).
Fold back the seal over the form, exposing the area of the drysuit to be cleaned and the inside of the seal, also to be glued.
Lightly sand the surface of the seal to be glued and clean with cotol.
Brush on a thin, even layer of Aquaseal onto the wrist seal and the drysuit area up to the masking tape (use the 3-to-1 mix with Cotol for fast drying).
Let dry completely.
Brush on a second layer of Aquaseal. If you're not in a hurry, don't use the cotol mix.
Let the glue dry to a tacky touch and roll the seal back over the drysuit area. Go slow and roll even and you won't get any wrinkles. Press firmly
Allow to dry. Remove tape. Go diving!
Again, others will make possibly better suggestions, but this has worked for me.
