I spent the better part of my career at Merrill Lynch (MER Quote - Cramer on MER - Stock Picks) as a vendor of leverage
primarily to hedge funds
. You might recall one of them by the name of Long Term Capital Management. LTCM was a master of the use of leverage, which also led to its undoing.
or other financial institution
. Such credit arrangements are regulated by the Federal Reserve
through a series of regulations -- Regulation T, Regulation U and Regulation X. Of those rules, Regulation T contains the guidelines that govern the extension of credit by broker-dealers to customers, particularly individual investors who purchase and carry securities. To many people, Regulation T is simply referred to as the "Margin Rules."
The Margin Rules
There are many aspects to the margin rules that you must understand before buying securities on credit. I will discuss those rules in the context of stocks.



