Toast is indeed ideal for the classic BLT ~ and toasted home-baked wheat bread is even better ~ but for tomato-and-mayo-only, there's something to be said for the extra-sloppy redneck "kitchen sink sandwich" on plain white generic supermarket sandwich bread, with extra-juicy tomato slices and maximum mayonnaise.

Not a gourmet item, and certainly not especially healthy, but high in nostalgia value. Especially when a chunk of that white bread sticks to the roof of your mouth!

(That nasty square-slice white bread is also the best and only alternative in another context: freely issued for use as "napkins" with barbequed ribs!)