Windows and Doors
If Dracula's immigration to Britain can be read as an allegory about foreigners invading England, it seems reasonable that border-crossing in general will be important in Dracula. Individual homes are like mini countries for Dracula to invade, so Stoker spends a lot of time describing Dracula's entrance into various homes. The vampire is unable to enter a house where he hasn't been invited, which is why he spends so much time in the form of a bat hovering around Lucy's window, and why he entices her outside while she's sleepwalking so that he can drink her blood there. It isn't until he's gotten a wolf from the zoo to break through her window that he's able to enter her home and drink her blood in the comfort of her own bedroom.