Understanding the Scout Handshake
The left-handed Scout handshake is a formal way of greeting other Scouts of both genders used by members of Scout and Guide organizations around the world when greeting other Scouts. The handshake is made with the hand nearest the heart and is offered as a token of friendship. In most situations, the handshake is made firmly, without interlocking fingers, and many organizations only use this handshake when both people are in uniform. There are some variations of the handshake between national Scouting organizations and also within some program sections.
The 1935 Boy Scout Handbook says that "By agreement of the Scout Leaders throughout the world, Boy Scouts greet Brother Scouts with a warm left hand clasp."
All members share the left handshake, and when meeting other Girl Guides and Girl Scouts our Boy Scout, it may be used in conjunction with the Scout sign done with the right hand.
Meaning of the left-hand
Various sources have attributed the origin of the handshake, as an ancient sign of bravery and respect, to Lord Baden-Powell's encounter after battle with Prempeh I, or to earlier published works by Ernest Thompson Seton. There exist various versions of the Prempeh story, all centering around African warriors using the left hand to hold their shields and to lower it and shake the left hand of the person was to show they trusted each other.
According to the Ashanti warrior version of the story, then-Colonel Baden-Powell saluted them with his right hand, but the Ashanti chiefs offered their left hands and said, "In our land only the bravest of the brave shake hands with the left hand, because to do so we must drop our shields and our protection." The Ashantis knew of Baden-Powell's bravery because they had fought against him and with him, and they were proud to offer the left hand of bravery.