The research originates from a comment to the 1981 Stiglitz - Weiss paper. Specifically it is about the collateral role in the problem of credit rationing. The idea here analysed is that the posting of collateral by entrepreneurs could be interpreted as a signalling strategy about the "goodness" of the investment project; if this would be the case there could be a possibility for overcoming rationing. We present here a simple numerical example of a contracting game between entrepreneurs and banks, a case in which the strategy of posting high collateral is univocally associated with the entrepreneurs investing in "good" projects.