They are stating the London authorities are focusing on one particular 'Rucksack' (backpack) as the particular types terrorists use.
"W"rong The type of Rucksack they are limiting their view to is:
http://www.redoxx.com/catalog/day-packs/p_c-ruck.html
It is a military type issue backpack. However, the 'term' Rucksack could mean a lot of designs:
http://clipart.usscouts.org/library/Scouting_Skills_and_Activities/camping_gear/rucksack.gif
The Scout Rucksack
http://www.kaiserstock.ch/ausrstng.htm
The Recreational Rucksack
http://www.arucsystems.com/design.htm
An expeditionary Rucksack
THE POINT is I know what good people we all are and we will accept information readily and focus on 'terrorists' as described to us. There is no ONE definition of Rucksack. There is no ONE design. Then to realize as soon as the population is focused on a particular danger the terrorists are far to smart regardless any potential language barrier and they will switch the design backpack or suitcase or otherwise used.
In Israel.
The explosives.
Are delivered.
On the body.
Of the terrorist.
Let the authorities do their jobs and the best way to assist is to tell someone of your suspicions. It protects you as well and may save you embarrassment. We do not have the authority to take this on ourselves nor should we. We are the people the authorities are supposed to protect and they need to do EXACTLY that !!
Be safe.
Much peace.
Calgon take me away !