Most of the clogs that I have seen are at the very bottom, where the flex pipe connects to the dryer. There is a hose clamp there. Just loosen it, pull off the flex pipe and take out all the lint, coins, matchbooks and marbles. Then, re-attach it and check the outlet to see if you have re-established good air flow. If this doesn't do it, and you do have a section of the pipe that is horizontal, then that section has likely filled up with lint and is clogged as Harold said. If you can unclog this section, fine, done. Frequently however, this is not practical and most times I end up having to put in an entire new pipe because it is easier than trying to clean out a clogged one. Make sure your lint screen is working correctly, otherwise it will clog right back up again.