This is supposed to be a way to weed out those with fevers who in return might get others sick. However, analysts are saying that this method is not efficient because it does not account for people that have no symptoms. Also, not everyone has a fever with COVID-19. Some are proposing a scratch and sniff test since one of the earliest symptoms of COVID-19 are loss of smell. The customer would have to acknowledge what they are smelling in order to be let into the building.
Source: https://www.statnews.com/2020/07/02/smell-tests-temperature-checks-covid19/