I use copper rivets when extra strength is required, for example when fixing a grab handle to a case or bag designed to take heavy loads. By themselves they are immensely strong but when coupled with saddle stitched reinforcements they form the strongest of all leather fixing systems.
I punch a hole through the leather, push the rivet through and using the setting tool, set the washer over the pole of the rivet and bed it against the leather. The pole is then trimmed to size and again using the domed recess of the setting tool the end of the pole is hammered either into a dome shape or flat as required. They provide the strongest fixing, look attractive and never rust or degrade.