Cadillac 2005 DeVille - Manual (Page 27)

The shoulder belt may lock if you pull the belt
across you very quickly. If this happens, let the belt
go back slightly to unlock it. Then pull the belt
across you more slowly.
2. Push the latch plate into the buckle until it clicks.
The latch plates for the safety belts in each rear
seating position vary in size. If the center rear or the
left rear latch plate is inserted into the incorrect
buckle, the plate will not latch properly. Be sure you
are using the correct buckle and that the latch
plate clicks when inserted into the buckle.
If the belt stops before it reaches the buckle, tilt the latch
plate and keep pulling until you can buckle it.
Pull up on the latch plate to make sure it is secure.
If the belt is not long enough, see Safety Belt Extender
on page 1-25.
Make sure the release button on the buckle is positioned
so you would be able to unbuckle the safety belt quickly if
you ever had to.
3. To make the lap part tight, pull down on the buckle
end of the belt as you pull up on the shoulder part.
1-21