You will all probably have come across the problem wishing to install a package from the tree but having an overlay with the same version of the package, but different code. And you will all have hit google with keywords "mask package overlay". But there is no solution straight. You cannot mask packages on an overlay basis. One thing I always did is copying the ebuild to my own overlay and being happy. But what if there are some improvements, bugfixes introduced in the maintree ebuild, you won't notice them. This morning a simple but brilliant idea came up my mind, why don't use symlinks. Hey, sometimes clever brains need a longer time!! The only thing you have to be careful with is that in the /etc/make.conf your overlay dir must be the last in the ${PORTDIR_OVERLAY}.