An optical device housing has a post rotatably extending therefrom and a sleeve fixedly extending therefrom. The sleeve is disposed about the post and a knob is connected to the post. A nut rotatably engages with the sleeve and is configured to rotate with the knob. An adjustment screw is threadably engaged with the nut and engages with the knob so as to rotate with the knob. Rotation of the adjustment screw about a screw axis increases a frictional resistance between the nut and the sleeve.