Surface tension from the curved lid channels water into the holes without taking leaves with it.
Best way to keep leaves out of your gutters.
This will at least help reduce the amount of leaves you will have to clean up.
They must be brushed off from time to time or the debris that sits on them will disintegrate and eventually clog the foam or wire.
If you live in house that has any trees around it gutter guards are going to be a great investment.
Your job brushing aside any accumulated debris from time to time to prevent runoff from cascading over the face of the gutter.
The theory is similar to flat screens described above in that the insert will let water through and keep debris out of the gutter the top of these inserts are essentially flat when installed into a gutter.
The answer to this is going to be to install gutter guards.
It installs under the gutter ferrules to protect it from blowing away in high winds.
These guards range in price and usefulness.
With surface tension gutter covers water clings to the rounded nose of the guard and flows into the gutter while leaves and other debris fall off over the edge.
How they work a vinyl plastic or metal grid sits atop the gutter letting water in while keeping leaves out.
Small debris sometimes gets in but usually washes out the downspouts without a problem.
Make sure you especially trim the branches that overhang your gutters.
If you have a lot of trees on your property then another good way to prevent a lot of leaves in your gutters is to regularly trim your trees.
Surface tension guards work very well with leaves and other large debris.