Some of these lappys have fans that are on the bottom. Do these fans blow out from the bottom or what? Or do they suck air in?

Got a customer saying that his lappy is getting hot. Now on mine I use it on my kitchen table with a soft cloth place mat underneath it. Would this thing be not a wise thing to do because the fan is on the bottom whichever way is blows or sucks?

Because if there is cloth over the fan then circulation is not working at it's capacity?