The seat of a bicycle is attached to a post by means of a bracket and screws. The bracket has an opening into which the seat post fits and is secured by bolts. The seat post is typically 8 to 10 inches in length and fits into a round opening on the top of the bike frame. The post is held in place by a clamp with a bolt or a lever-operated clamp mounted to the frame of the bike. The seat and post are adjusted at the clamp point on the frame.
Position the bike so that it is upright and stable, allowing both hands free to work. Prop the bike with an attached bike kick stand or place in a bike rack.
Locate the clamp located at the point where the seat post attaches to the bike frame. The clamp will be made of metal such as aluminum and will surround the frame post. There will be either a bolt and nut or a lever for loosening the seat post.
Release the clamp by loosening the bolt. If the bike has a nut and bolt configuration, loosen the bolt until the clamp is free. If there is a lever on the clamp, push it open. If the clamp does not come free, rotate the latch counter clockwise to loosen.
Grasp the seat post and pull up to raise or push down on the seat to lower. It may be necessary to slightly wiggle or twist the post to make the adjustment.
Secure the post clamp again by either re-tightening the nut and bolt or closing the finger latch. Remember to turn the latch clockwise if loosened earlier before closing.
Test the seat by pushing down and attempting to twist. The seat should not move. If the seat does move, the clamp will require further tightening.