keeping shifters up

my shifters keep sliding down my handlebars. I tighten the screw and retape the cables everytime I move them back into place, but they keep moving down. Is there a trick that I am missing? thanks

What type of shifters? What type of bars (straight or drop)? Do they tighten with a flat-blade screwdriver, phillips screwdriver, or hex wrench?

sorry for the lack of info. they are shimano brake shifters, the screw is a phillips, and the bars are drops. they are tiny little screws that I am afraid of stripping

I thought the screw was inside the hood- can you post a picture?

STI brifters on drop bars? Chicken Little is right. The clamp attachment is a 5 mm allen key under the hoods but outside the levers. There is a groove for the wrench on the outside of the lever that you'll see when you roll back the hoods from the front. You may need a special allen wrench to tighten it, since it takes a long reach to reach the bolt, and then you need a longish L shape to torque it adequately. It's a pretty hefty bolt - no danger of stripping it.

thanks, I thought it was the little screw on a metal clamp. I was wondering if it was for that or just to hold some plastic piece to another plastic piece.

oh and just to say, these are the shimano r600 short reach shifters.

Thought I would update on my triflings as a bike mechanic (or not). yep there is a bolt in the front that I could not see with my myopic vision. The Shifter grip is even grooved to fit an allen key. I only have short ones but I was able to tighten the shifters so that they would stay up.

thanks for your help. My bike mechanic book is in a state far, far away.