If you are riding on a street you do not have to lock your bicycle fork, but riding will be easier if the fork is locked. The front of the bicycle will go up and down less if the fork is locked and pedaling will be easier. If you are riding on a street or a trail, you may adjust your fork either all of the way up, all of the way down, or anywhere in between. You may do this while sitting on the bicycle. Do not do this while moving on the bicycle because you may get hurt. You may adjust the fork at any time you choose. Hope this helps.