I uses these "wire thingy's" when fitting my child's booster seat into the
front seat.  The booster seat really wants a "lap belt" going through the
underneath part of the seat.  If you take the seat belt strap coming from
the ceiling section of the car and run it through the "wire thingy", then it
becomes an effect "lap belt".   No need to run the lower belt (that attaches to
the frame next to the seat) through the wire.

I hope that is what it was intended for!

Jim
'90 Multivan