how do the seat belts lock?

[CanYouToyota]

Hello, i did a quick search in the forum and didnt find anything.
i'm doing a little maintainence on a 1990 toyota camry DX and it doesnt have any airbags and the seat belts dont lock. i havent tried hard braking and trying to pull it though. but i can swifty yank the seat belts and they dont lock. are they malfunctioning?
i dont know much about this car and if the auto seatbelts are optional or not. but it comes with single point automatic shoulder belts.

just a few pics from maintainence.















my family is the 2nd owner of this vehicle. the first owner never really cared for the car as she only uses it occasionally when shes out of state.

its a comfortable little car. i dont think its any much larger on the inside than an 01 civic sedan, but it's definitely more comfortable.
the suspension is cushy and power is adequate; alone at least. it'll probably be more than adequate once i get this little maintainence done.

[atobe]

the seat belts came in AUTO in the states only it seems like the rest of the world got the regular 3 point belts. you can try pulling on them really fast and see if they catch... but usually stomping on the brakes is the best test. and you should always use them with the lap belt also

[typesix]

The seat belts(shoulder and lap) will not lock if you pull on them fast, they have what's called inertia reel belts. They will lock if the car body experiences a very fast stop. The auto shoulder belts were also used by other makes, these systems bridged the gap between the regular 3 point belts and the introduction of airbags in conjunction with the 3 point belt.