Mason bees are commonly mistaken for honey bees as they look somewhat similar. However there are a number of differences that will help you determine what kind of bee you are dealing with. Mason bees are a solitary bee and are usually seen in small numbers from several to a couple dozen, whereas honey bees typically come by the hundreds and by the thousands. Mason bees also are darker in color than honey bees, have longer antennas, a shorter abdomen, and are slightly smaller.
I have often seen mason bees make their home in the weep holes of brick structures. These small weep holes provide ventilation and allow moisture to escape. Stuffing wire mesh into the hole can be effective in keeping bees out while still keeping the brick breathable. Sometimes in early spring, as the mason bees emerge from hibernation a couple can get trapped inside your house. This usually is nothing to worry about and may only continue for a week or so.
Mason bees are not aggressive and pose little threat in damaging your home. Like many species of bees, the male does not sting. The female typically will not sting unless squeezed in the hand.