Traditional bridge design has an inherent flaw—the strings have to be tied on. As a result after they leave the hole in bridge they are pulled upward before they reach the saddle, and this considerably reduces the ‘break angle’ over the saddle, which in turn has a deleterious affect on the sound.
A neat and simple solution to this problem is to use ‘tie blocks‘, aka ‘beads’. A string is threaded through and tied to a bead before going through the bridge on its way to the saddle. There are three holes and a groove in the bead, which allows this to be done easily, tidily and securely. When the string emerges from the hole it goes straight from there to the saddle, improving the break angle.
An incidental benefit of the tie block system is that the tying can be done away from the guitar, thus reducing the risk of damage to the soundboard.
Other solutions have been tried, principally making additional holes in the bridge, but these are quite fiddly to use, not very tidy, and must clearly weaken the bridge to some degree.