Why don't we "lock" the seat belt when using a booster?

[wencit]

The other day, I drove DS2's friend home from school in my Graco Nautilus. He is 5 1/2 years old. I noticed as the friend was getting in, he pulled the seat belt out all the way, then retracted it in order to "lock" it. Never occurred to me to do that, and it seems like a smart idea to prevent kids from squirming around (which is the big concern with boosters), right? Should I start telling my 9 year old (who sits in a LBB) to do that as well?

Thanks in advance!

[Simon]

Yes, sure you can do that. We do when our kids are younger/booster training and it does help keep them in position and if they do try to move, it reminds them not to lean/reach far over. If your 9yo would benefit then I would go ahead. I don't know of any down side to locking the belt. I don't lock it on my older son mostly because he has a bit of claustrophobia and it bothers him when he can feel it tight on his chest all the time.

[Joolsplus2]

Yeah, it used to be a very common recommendation, especially for younger wigglier kids (though mine leaned out of the belt, it retracted, and he couldn't get back in...that was a weird thing!). Harmony seats routinely recommend to lock the belt. And given how far some little kids fling when you brake hard, it seems like a locked belt might be a good idea for them.

Some vehicles recommend NOT locking them, though I *highly suspect* they don't want you to 'install' your boostered child and strangle them and sue the carmaker, rather than it's UNsafe to lock it (it's gonna lock in a crash either way, it truly should not matter if it's pre-locked, though there may be some reason to read harder if you have inflatable belts or pre-tensioners, you don't want to mess with complicated computerized belts, that's my caveat on that).
And sometimes the tedious act of getting the belt out of a booster makes you never, ever want to lock it (Frontier, it happens a lot, and it's a 5 minute ordeal to move things around enough to get the belt to retract fully and unlock, while it's all hooked in the belt guides and armrests. Nightmare.)