PBJelly is a part of the PBSuite package of programs. PBJelly can be used to try to close or shrink gaps that may be present between contigs after scaffolding.
The official documentation is availible at: http://sourceforge.net/p/pb-jelly/wiki/Home/
Most of PBJelly can be configured through an .xml
protocol that you have to create with a text editor. It is best to put this in the directory where your output is going. Below is an example of how this xml protocol can look:
<jellyProtocol>
/path/to/reference.fasta