What is a good knee pad that don't slide around while crawling around in crawl spaces ?

I have a cheap pair from Harbor Freight, the red and black ones....I use them on the boat cause I need to jam my knees into the sides when hauling pots, and when kneeling due to knee replacements....they've held up a year so far and don't move around, can't say about crawling in crawl spaces, I'm done with that, lol

Some pants have a pad pocket built right into them I know the 5.11 work pants often do. I use the narrow gardening pads and I clip that on my bucket handle with a piece of cable.

Carhartt, Dickies and Duluth all make double front pants also, that have the pockets for knee pads. Some are designed better than others.

I have a bunch of new ones I never wore I should list them in the Shed.

Years back I bought a bunch of foam GI knee pads, that would roll up and go into the knee pockets of those pants. Very light and thin, comfortable to wear.

I bought some hinged Klein brand at lowes that stay up pretty well and. I can even crawl a little on the knee that was replaced last April

Carhart's are good. The pads are pricey but they last a lifetime.