Clause 12.1 sets out procedures to be followed for the measurement of the works and valuation for payment. Clause 12.2 provides for the method of measurement to be as stated in the Contract Data, or if not so stated then in accordance with the Bills of Quantities or other applicable schedule. The Employer's fundamental obligation under the FIDIC as in other forms of contract is to pay the Contractor the price for the work contracted for in accordance with the payment terms of the Contract. Clause 14.2 in the 2017 forms contains detailed provisions concerning advance payments. Before any advance payment is due, the Contract Data must specify an amount. In order to prevent the Contractor from taking the advance payment but not proceeding with the works he must provide, at his own cost, an advance payment guarantee in an equivalent amount and in the relevant currency.