The law in simple terms
A hearing is held before a magistrate who determines the value/equity and approves the bond.   Witnesses may be called to testify, usually that they own the property and that they understand the  responsibility they are undertaking.

California Penal Code Section 1298
“In lieu of a deposit of money, the defendant or any other person may deposit bonds of the United States or of the State of California of the face value of the cash deposi t required, and these bonds shall be treated in the same manner as a deposit of money or the defendant or any other person may give as security any equity in real property which he or she owns, provided that no charge is made to the defendant or any other person for the giving as security of any equity in real property.”
“A hearing, at which witnesses may be called or examined, shall be held before the magistrate to determine the value of the equity and if the magistrate finds that the value of the equity is equal to twice the amount of the cash deposit required he or she shall allow the bail.”
“The clerk shall, under order of the court, when occasion arises therefor, sell the bonds or the equity and apply the proceeds of the sale in the manner that a deposit of cash may be required to be applied. The country treasurer shall, upon request of the judge, keep the deposit and return it to the clerk on order of the judge.”