Isometric Squat?

I’m trying to find a way to do a squat isometrically, for vertical jump…Other than simply overloading the bar so I can’t move it - I don’t have a spotter.

How would you do it? Doesn’t have to necessarily mimic the squat, more so mimic jumping…
I’ve read a rope or a band is good for this, but how do you use a rope or a band to do an isometric squat?

Thanks

Push the barbell against the pins in the rack at a given height.