What is the part of the backpack (for eg.) that's held to shorten or lengthen it? See detail for image.

I would call those adjustabelts.

Not the whole belt, just the part (the hard plastic that the strap goes through in one way out the other) that you hold while you pull the strap.

They are called strap adjusters, or side release buckles, Both terms are used in the industry and both are correct.

@zenvelo Do you have a link for that?

@zenvelo By the way buckle is a different thing isn’t it? re. “or side release buckles”

I don’t use back packs.

Edit redacted.

A buckle.

Ok. What is the other side called @RedDeerGuy1?

@Dutchess_III I don’t know. Maybe a clasp? Or a widget or whatchamacallit? Belt adjuster? Zenvelo is right. Edited.

@flo if you google backpack parts you will see the same plastic piece that the straps go through described in different ways. Both terms are interchangeable, one is not more or less precise than the other.

@zenvelo And re. my last 2 posts?

@RedDeerGuy1 Not the buckle. See here:
https://tinyurl.com/y3lxfar5 (travel bags Google images) The hard plastic in the left-ish part of the shoulder strap.

That’s Bing.
Don’t confuse us.
~

Lock sliders.