The 12-hole tie block bridge has advantages
- More secure attachment of strings
- Better break angle of string over saddle and so better tone
It is a bit harder to attach new strings however.
First you need to remove the saddle in order to get easy access when threading. That means you have to loosen (or remove) all the strings even when you want to change only one as you cannot remove the saddle without doing so.
You will see in the pictures that I use masking tape and plastic to protect the soundboard while I am working. You particularly need to protect the soundboard immediately behind the bridge as the ends of the strings and your nails are almost certain to rub against it while threading and tying.
Second, you need to thread all 6 strings loosely through the tie block before replacing the saddle. I usually replace one string at a time to prevent a tangle with with the saddle removed this is not feasible. So you have to manage the inevitable tangle.
I thread the end of the lower string through the tie of the string above so as to achieve the maxiumum possible security of the string. You will see in the picture that I use a figure of 8 knot on the first string which is the last one to be tied as it obviously cannot be secured as the others are.