1. A LOCKING DEVICE FOR STRAPS HAVING TWO ENDS TO BE JOINED, PARTICULARLY WATCH BRACELETS, COLLARS, BELTS AND THE LIKE, COMPRISING A SUBSTANTIALLY FLAT BUCKLE MEMBER HAVING MEANS FOR SECUREMENT TO ONE STRAP END SO AS TO PROJECT THEREFROM IN THE PLANE THEREOF, AT LEAST ONE PROJECTION PROTRUDING FROM THE PLANE OF A PORTION OF SAID BUCKLE MEMBER FOR ENGAGEMENT IN A HOLE OF THE SECOND STRAP END, A SLIDER HAVING CHANNEL-SHAPED GUIDES AT ITS SIDES FOR SLIDEABLY EMBRACING ONLY THE EDGES OF SAID SECOND STRAP END, AND A CENTER PORTION BETWEEN SAID GUIDES RAISED TO PROVIDE A SPACE BETWEEN SAID GUIDES FOR