I take it you mean they bleed because they reopen?
If they are gaping for more than around a centimetre(or have bled for more than ten minutes when you've put pressure on them)then you should get them seen to see if they need to be stitched. Though many doctors will only usually do this up to 8hrs after you've cut, some do it up to 12 depending on the circumstances but hardly any do it after 24hrs. So, by the time it is now and the time you posted I'm guessing it is over the 8hr mark at least.
You could steri-strip them closed. You should do this when they're not bleeding (or the strips won't stick) and within 24hrs of the cut being made. You can either buy them from a Chemist or make your own using medical tape (Micropore usually) but these aren't quite as clean though can be as strong.

Butterfly bandages are best for closing a long cut.Use an adhesive strip (such as Band-Aid) to provide continuous pressure. Always put an adhesive strip across a cut rather than lengthwise. A butterfly bandage (made at home or purchased) can help hold cut skin edges together:
- Using a clean scissors, cut a strip from a roll of 1-inch adhesive tape and fold it sticky side out. Cut notches into the tape as shown in illustration A above.
- Unfold the tape; then fold the notched pieces together, sticky side in as in illustration B above. The center of the tape will not be sticky. Keep the part that will be over the cut clean.
- Place one end of the tape on the skin. Then pull the other end to close the wound tightly as in illustration C above.
- If the cut is long, use more than one bandage.
These however may not work too well if it is in an area where the skin moves a lot/ is under a lot of strain as it will tend to pull the edges apart (areas like this are ones close to your joints ie. your wrist)
Also, apply anti-bacterial cream to the cut (don't do this if you're using stristrips as then they won't stay stuck!) and put a dressing over the top. Change the dressing about every day or so and keep the cut clean. This will greatly reduce the chances of infection, will protect the wound making it less likely to open up and it will also absorb the blood if it does get knocked and bleeds a bit.