Why do banks need security cheques when handling mortgages?

A security cheque may be needed when you apply for a mortgage in Dubai. This protects the bank if you are unable to make your repayments on time. The check, which is typically not dated, serves as collateral for the full loan amount. The bank may attempt to cash the cheque and fill in the date if you fail on your mortgage. 

About Security Cheque

It is a bank practice that one should issue a security cheque in Dubai for loans like mortgages. It acts as a guarantee. You give a cheque for the borrowed amount of money, which is usually undated. Failure to make back your loan lets the bank cash (date) at its convenience. This provides them with the legal edge to collect assets from you, up to and including foreclosing on your pledged assets. Bankers do this as an insurance policy on their investments.