Is it the right time to lock your investments in a property ?

Looking at the real estate sector in the US, it is said by many people that by locking the property one can save a secure amount of his/her property. Yes it is true, as by locking the property the owner of the property will claim and enjoy the amount which is decided earlier, no matter what the market value is. If the market value falls, then the owner can sell the property at the fixed price which was decided earlier. If the market condition improves then also the owner is in benefit as there is no obligation to sell the property.