Just to clarify:
TETHER is for the strap behind the seat, reducing head excursion.
LATCH is the lower anchors in seat, used instead of the seatbelt to install a CR.
Many people confuse the two or use the terms interchangeably.
Dealers CAN install a TETHER. Only a very few makes, models, years can retrofit LATCH.
not to nitpick, but... for the sake of clarification:
TETHER is the
STRAP the runs from the top of the shell to the tether ANCHOR (TA). the tether comes already installed on the carseat, while the TA is the hook that is bolted to the car.
LATCH =
Lower
Anchors
and Tethers for
CHildren. it is an acronym for the carseat attachment system which includes
both the lower anchors AND tether.
the dealer does not install a TETHER. they install the tether ANCHOR (TA). it is the lower anchors that can not be retrofitted on most cars.
and yes, the nomenclature is confusing. they really should have thought of something more systematic instead of something "cutesy". i mean, technically, the belt that 99% of us refer to as a "LATCH" belt should really be called the "lower anchor" belt, because it fastens to the lower anchors and is completely separate from the tether.
i hope that clears it up... confusing, INDEED!