This is a short VDO demonstrating wash over operation with washing tool.
If you cannot see it, please find it via youtube here http://youtu.be/2kIQFuyj_bQ
When the wellbore is collapsed and there are formations over the fish, you need to wash over the top of fish in order to clear any sands or debris.
The washover pipe is used for this operation. It will slip over the stuck pipe and drilling mud will flush out any debris in the annulus between pipe and wellbore. When the top of fish is clean, you can run in hole with fishing assembly to engage and recover the fish down hole.
Note: This VDO is a part of Weatherford Fishing Service.