Seriously, public trashcans seem to be an obvious place to put a bomb. How many bomber movies had the bomb in a public trashcan? Maybe frequent checks of these cans at public events are necessary. Given that pedestrian trash is rarely large & bulky, trashcan openings can be much smaller. The cans can be placed in the open so that they are easily observed by all. They should be emptied just prior to a public event. If these bombs were on timers, then they could have been there for hours.
If you picture the thumb and index finger of your right hand...
poised just like you would grip anything...
in my case a match...
one of my powder test batches flashed and charred all the hide right off.
Doctor at emergency room said he was on the verge of buying a Lee reloader and I changed his mind.