If you are new to hedging and topping please take a moment to check out some studies and articles (below) that emphasize the importance of implementing a regular pruning regimen.
Comparison between hedged and non-hedged– http://walnutresearch.ucdavis.edu/2003/2003_171.pdf
Citrus- http://aggie-horticulture.tamu.edu/citrus/pruning/L2308.htm
http://www.crec.ifas.ufl.edu/extension/trade_journals/2006/DEC%202006%20hedging %20topping%20skirting.pdf
Pistachios- http://fruitsandnuts.ucdavis.edu/files/73692.pdf
http://hortsci.ashspublications.org/content/30/7/1369.full.pdf
Prunes- http://ucce.ucdavis.edu/files/repositoryfiles/2007-56.pdf-79182.pdf
Stone Fruit- http://ucanr.edu/sites/fruitreport/files/163196.pdf
http://www.goodfruit.com/Good-Fruit-Grower/February-1st-2007/Short-trees- reduce-labor-costs/
Pecans- http://m.westernfarmpress.com/tree-nuts/more-profit-potential-southwest-tree-hedged-pecans