Most wastes will be available in both slotted and unslotted forms. The type of waste you need will depend on whether the basin has an overflow built-in it or not. The pop up waste installation tool is only designed to work with slotted, pop up wastes.
The overflow of a sink assists with drainage as it allows air into the drain when the sink is full. A sink without an overflow will act like a vacuum when full and will drain slower, therefore if you do have a built in overflow it is a good idea to ensure it is working correctly.
Slotted wastes
Most sinks will have a built-in overflow; these will require slotted wastes. This is so that when the water passes through the overflow it can flow through the holes into the drain.
It is important to ensure the slots of the waste line up with the overflow so the water can run efficiently, the pop up installation tool is designed to make this job easier.
Unslotted wastes
Unslotted wastes do not have any holes and should only be installed into systems without an overflow.