A withdrawal lock is applied based on the value of the qualifying investments that have been pledged for you to borrow against in the relevant accounts that you selected when taking out the loan. While you will still be able to buy and sell shares within these accounts you will not be able to transfer or withdraw cash to the value of the lock from these accounts.
This is known as a collateral lock.
The term collateral refers to an asset that a lender accepts as security for a loan. The collateral acts as a form of protection for the lender. That is, if the borrower defaults on their loan payments, the lender can seize the collateral and sell it to recoup some or all of its losses.
Securities, refer specifically to financial assets (such as stocks or shares) that are used as collateral