Combine ingredients in a rocks glass with ice and stir to serve. If desired, garnish with a lemon wheel.
This is a very forgiving cocktail and can be made to your taste: Some prefer equal proportions of scotch and Drambuie; others half the Drambuie; still others double the scotch. For a "Smokey Nail," make sure you use a heavily peated scotch (e.g., Islay single malt). As variations, substitute bourbon for the scotch, known as a Rusty Spike or Rusty Bob; you can also substitute mezcal or rye whiskey for the scotch.