Verminstar; As Adept says, the external borders of the Schengen zone are secure but within there are no border checks.
Do you have locks on every door in your house? Do you need a key to get from the living room to the bog, a passcode to go upstairs? Or, like most people (apart from the tinfoil hat brigade

) do you just have locks on your front and back doors and windows and allow members of your household to move between rooms freely?
Confusion over the Schengen zone, "freedom of movement", EU migration, nonEU migration, refugees, illegal immigrants etc is common amongst leave supporters but they are very different things.