Advantage over Banks
Banks lend money. That is what they do. For certain customers, banks also provide bonds. However, when you get a bond from your bank, they treat it like a loan even though they have not parted with any cash.
You provide the collateral security, pay the charge and they give you a piece of paper. But you can't buy a site or pay your bills with that piece of paper.
Then, when you want to buy a site or need more working capital to expand your business, the bank will take account of the outstanding bond when assessing how much more they can loan to you.
A bond from Construction Guarantee leaves your bank facilities untouched. Your credit facility can then be used for the purpose intended - to develop and grow your business.