Connexons: These are proteins that make up gap junctions. They're like the actual door frames and doors in our analogy.
Tight Junctions: These are areas where membranes of two adjacent cells join together forming a virtually impermeable barrier. It's like sealing off a room so nothing can get in or out.
Desmosomes: These are structures by which two adjacent cells are attached, formed from protein plaques in the cell membranes linked by filaments. They're like heavy-duty bolts securing two things together.