Thumb Slap

The thumb slap technique mimics the snare drum and adds to your playing a pronounced rhythmic layer.
Thumb slap is performed by hitting the 6th string (also the 5th or the 4th strings in some cases) with the inner side of your thumb, an area
between the nail and the joint:

There are 2 slightly different thumb positions for hitting strings. I call them the outward position – when the thumb is curved a bit outwards (or up), with the thumbnail located above a string (as shown in the example bellow), and the inward position – when the thumb is curved inwards (or down) with the thumbnail located bellow a string.
In the illustration bellow, the blue line shows the curve of the thumb:

Each position is used depending on what bass string is picked next after the thumb slap.
In the next lessons I’ll explain them in detail.