Even today, they're of a special design to limit their use as extra shrapnel around a bomb. The UK does reasonably well at "hidden" security features. Another

Even today, they're of a special design to limit their use as extra shrapnel around a bomb. The UK does reasonably well at "hidden" security features. Another type are "decorative" features -- like the word "Arsenal" outside the football club, or the ponds in front of the Scottish Parliament building -- which just happen to be in the right place and of the right strength to prevent vehicles crashing through.