Remove the crusts from the slices of bread (freeze to grate and use as Rissole fillings later on).
Along the middle of each slice, spread a little mayonnaise and avocado.
Place long, thin strips of cucumber on top and roll tightly.
Cut in thirds, turn up and place tightly into the lunchbox, with seams touching each other so as not to fall apart.
Use any number of different fillings; shredded chicken, boiled eggs, asparagus, ham, cheese, grated carrot etc.