the dogs 414 outwardly since at this point the packer setting subassembly 400 is still within the liner l the dogs 414 will move out against the inner surface of the liner l pressure is then further increased to open the upper bypass port 612 as shown in more detail in fig1 and 17 that is as pressure is increased on the upper bypass port 612 this pressure eventually shears the indicating ring shear screw 660 which releases the indicating ring 610 to be driven downwardly this opens the upper dart bypass port 612 for cement flow which passes through the annulus and back into the main bore through the lower bypass port 614 thereby bypassing the lower dart 656 and providing an indication for the operator that the dart has seated and the bypass flow of cement has been established if the upper bypass port 612 does not open the pressure is increased until a blow out plug in the lower dart 656 is ruptured when the upper dart 658 has seated against the lower dart 656 this again blocks flow through the bypass ports 612 614 or through the blow out plug after completion of the cementing the annulus surrounding the perforation assembly 500 is filled with cement except for the flow paths.