Slice the pickle in half lengthwise.
Use a spoon to scoop out the seeded center portion, leaving some pickle flesh for support.
Pat both halves dry with paper towels.
If needed, trim the bottom of one pickle half slightly so it sits flat.
Spread mayonnaise along the inside of the hollowed pickle.
Fold the turkey slices and place inside the pickle.
Cut the tomato and onion slices in half and add them to the sandwich.
Cut the cheese slice in half and layer it inside.
Add the romaine lettuce leaf.
Place the top pickle half on the sandwich.
Insert toothpicks through each end and one in the center to secure the sandwich.
Slice in half and serve immediately.