Fork In Pega:

Fork Is Used To Decision In a Flow Using When Condition

For Each Condition We need to  Create When Rules In Pega 6.1 and Prior version On Pega 

There was Separate Flow Shape Available That is Fork

In 6.2 On wards Fork has been Included one Of The Option Decision Shape

=>Create When Condition For Property 

"When.Property=Value"

Another When Condition 

"When.Property=Value"

=>Go To Flow

Double Click On Shape  "Decision Properties  select Type="Fork"

=>Click on "Outgoing Connector" 

Condition Type=When

When=property Name