challenge people
Challenging is a physical security measure that is appropriate in certain situations. Places challenging people for security measures is appropriate are prisons and military sites.
Speed.
firewall
firewall
yes
Security seals are a security measure taken to prevent tampering with containers or evidence. The company Security Seals is a leading manufacturer and seller of all types of security seals.
There are a variety of shades on the market that are stylish and still provide a great measure of security.
Low voltage lightning installation is a valid security measure, any lightning around the area can still serve as a security measure since it is known to repel any malicious activities in someone's vicinity, but compare to low voltage wiring low voltage lightning can be less effective.
Physical access restrictions
an example of a physical security countermeasure would be a tether on a digital camera displayed for sale.
Metre to measure its length. Possibly centimetres to measure its height if a garden fence but metres if a security fence.