The SOS redouble is a redouble calling on the bidder's partner to rescue the bidder from a potentially disasterous contract. Some example auctions are:

1 club     double   pass   pass
redouble
The one club bidder might have opened one club with two or three small clubs. He is asking his partner to rescue him.

1 heart   2 clubs  double  pass
pass       redouble
The two club bidder has overcalled with a weak suit and needs help getting out of a bad contract.

pass   pass   2 hearts   double
pass   pass   redouble
The two heart bidder has probably opened a weak two on a very poor five card suit and wishes he had not.

The Kock Werner Redouble is a convention invented by a Swedish partnership of Mr. Rudolf Kock and Mr. Einar Werner. In this case it is the partner of the bidder who redoubles when the bidder's low-level overcall has been doubled. The redouble in the auction below is for takeout, and strongly indicates a shortness in the suit bid by his partner if the partnership is utilizing the Kock Werner Redouble.

2 hearts   pass   pass     double
pass        pass   redouble
The redoubler probably has a void in his partner's suit (hearts in this case) and wants him to pick a side three card suit.

A partnership can use either or both of these conventions. However, they must discuss using them first