Whipstocks
Advantages
It provides a controlled hole curvature
at the onset
Jetting bit
Advantages
Several attempts can be made to initiate deflection without
pulling out of hole
A full gauge hole can be drilled from the beginning
Disadvantage
The technique is limited to soft-medium formations
Severe dog-legs can occur if the jetting is not carefully
controlled
On smaller rigs there may not be enough pump capacity to
wash away the formation