On gas dryers, ALL VENTING MUST BE METAL. NO PLASTIC. All Building Codes prohibit the use of screws in joining dryer venting for the exact reason mentioned, they catch the lint. In general, vents should not run vertical if possible, and should not have more than a couple of bends. Each 90* bend will reduce the maximum length of the allowable dryer venting by several feet. Contact your dryer manufacturer for specific information on your dryer. General Electric is 1-800-626-2000. Also, vacuum out the inside of your dryer between the lint screen and the vent. You will need to remove the front panel to do this, but you usually will find a buck or so in change when you do it! *grins* Have fun.