CRAFTBOOK-2913 - Reported by FuRiouSOne

CraftBook version 3.8-SNAPSHOT:3621-20a92c8,master

Build your bridge one block above ground
https://www.dropbox.com/s/5wthl8t7hv6vvaz/2014-02-15_23.53.40.png

Fill the sign with blocks and retract it
https://www.dropbox.com/s/kl3tzo37bbokrfe/2014-02-15_23.53.47.png

Place valuable blocks under sign shown in screen shot
https://www.dropbox.com/s/o100pqkdtbbz7xu/2014-02-15_23.54.15.png

extend bridge and the non valuable blocks (stone) loaded into sign extend into the valuable blocks which can be mined and repeated duplicating what ever block you wish just using stone or any other non valuable block in game.
https://www.dropbox.com/s/y6xa61s0lqih1p0/2014-02-15_23.54.57.png

Settings:

safe-destruction: true

bridge:
    enable: true
    allow-redstone: true
    max-length: 30
    max-width: 5

Basically when you place a block under or over the sign the sign will ignore the (stone) blocks issued to the sign and turn them into whatever block type you placed above or below the sign after filling it.

Comment by me4502

I would recommend to not allow valuable blocks to be used in bridges and doors.
This is a rather large issue to fix, as it requires implementing block bags.