In a normal scenario (when using a #8 wood screws pan head) a normal 3/16” wood drill bit SS is enough to drill extra holes into the male and or female bracket. Just remember to respect and use the die line (the raised ridge on the bracket) and to drill the holes along that line.
When only making a few holes you can do it by hand with a normal drill. If you drill many holes, a drill press is recommended.
If this is your first install and you don't have all the required bits, you may also want to purchase our Installation Bit Pack along with your brackets to set you up for installation success.