guards and dealers definitely produce use-values; otherwise no-one would pay them. But, at least in Marxian political economy, they do not produce surplus-value. The guard simply preserves property rights, while the cashier transfers them. The worker who produces surplus-value -- who might be a service-worker, contrary to Adam Smith -- actually creates new property rights, which are held by the employer.
^^^^^^^ CB: If they produce use-value, then they produce exchange-value. Use-values are the thing in which exchange-value exists. If they produce exchange-value , then they can be exploited out of surplus-value. The use-value a security guard produces is the absence of having some means of production or commodities stolen, that is preservation of possession, preservation of appropriation of the commodities and therefore preservation of surplus value for the capitalist. Appropriation or possession of the commodities is just as much a necessary condition for expropriation or exploitation of surplus value as the labor producing the value.
