How does sigma dg 28-300 zoom lock work

[lakeman]

Hello. I just got a Sigma DG 28-300mm lenses for my Canon Rebel XT. I am told that the lenses has a zoom lock. Where is it? How is it used?

 

[Guest]

Sigma zoom lock, small toggle on base of lens that stops the zoom lens opening under gravity, it locks the Zoom at smallest mm setting or all the way in!