Probably a dumb topic, but the contents keep slipping out of my sandwiches.
I'm a vegetarian, so a typical sandwich means sliced avocado, cucumber, tomato, sprouts, some shavings of hard cheese, red onion slice. Maybe a little mayo. Bread is cut from a long brick-oven Italian loaf, then sliced in half lengthwise.
I just realized most of those ingredients are slippery in themselves! I guess a harder grip on the bread may be the only cure.