#5 - ARM LOCK
This is the putting grip you will see used by Matt Kuchar, and it's a great method for those who previously used to anchor the putter before it was outlawed in 2016.
With the arm-lock putting grip, the handle of the putter locks against the inside of the left forearm (for right-handed golfers). This union should not separate at any point of the stroke (and this holding of the putter handle against the forearm does not constitute anchoring - it is legal under Rule 14-1b).
The major con with this stroke, however, is that it requires a putter with a minimum of 6 degrees of loft and adequate length for the handle to rest flat against the inside of the left forearm.