One side won't focas - Barska Optics Optics

You don't say what model binoculars you have, but there are two possibilities (well, three, but the third one is that your binocs are broken - lets try the other two first!)

Some very fine binoculars have individual focusing for each eyepiece. You focus each side for your eyesight. If that's the case with your binoculars, there won't be a central focusing control.

If you DO have a central focus knob, it's possible that your binoculars have a "diopter" focus on one or the other eyepiece. Look at the rim of the eyepiece for a marking that looks like "+ . . . | . . . -" or something similar. What you want to do is focus the binocs using the central control so the the UNMARKED eyepiece is in focus for you (close one eye to focus), then switch eyes and focus the marked eyepiece by rotating the eyepiece rim until both eyes have good focus.

Binocular manufacturers do this because many people have better vision in one eye than the other, and many people also prefer to use binoculars without their glasses. Hope this helps.