If you mean a quad rail handguard;
You don't always need a wrench to install quad rail handguards, or need to spend a fortune on quad rails because of the name on them. It depends on which model of the M&P 15 you get that will determine overall what you get for handguards and the installation method needed.
For example the carbine OR model can use these >
http://www.primaryarms.com/product.s...4&categoryId=1 $29.99 and just as good as anyones $200.00 item with their name on them, especially for the price. Rock solid, installed in about two minutes, and drop in with no wrench needed. You just pull down on the delta ring, take off the factory handguards, snap these in place and tighten down the four screws and your done.