I just happen to come along and discovered certain defensive moves as I was playing against several opponents. I have named these defensive patterns as "the Y defense" and "The Corridor of Risk".
The "Y" defense" is a defensive pattern, where you have 3 or more pieces that form into a letter "Y". In a much more supported Y defense, this consists of 3 vertical rows of blocks or spaces, 2 pieces are consecutively 1 after the other. 2 back to back pieces form 1 wing of the letter Y, while another pair forms the other wing...2 more back to back pieces form the trunk or the stem of the Y joining the 2 rear pieces of each wing... You can also choose, if you wish, to reinforce each wing from their flanks.
The "Corridor of Risk" is another defensive pattern, which is similar to the Y defense. The difference is that there is a long row of spaces/blocks between each wing of 3 or more pieces, wherein 2 walls are created. Hence, it looks like "a long corridor". For your opponent, it can be intimdating, that if the opponent's pieces wish to enter, they would have to take the "risk", of the "walls" not collapsing in on them... (one way of creating claustrophobia on your opponent.... Hehehehe)
Actually, any defensive move, if not played right, can also create risk for your defense. The only way for these manuevers to succeed is by having your supporting pieces nearby to back up these defensive moves and patterns.....
Good luck, enjoy and have fun!!!