diff --git a/nhf/materials.py b/nhf/materials.py
index c752cd4..7ac4c26 100644
--- a/nhf/materials.py
+++ b/nhf/materials.py
@@ -8,7 +8,25 @@ def _color(name: str, alpha: float) -> Cq.Color:
     r, g, b, _ = Cq.Color(name).toTuple()
     return Cq.Color(r, g, b, alpha)
 
+class Role(Enum):
+    """
+    Describes the role of a part
+    """
+
+    # Parent and child components in a load bearing joint
+    PARENT = _color('blue4', 0.6)
+    CHILD = _color('darkorange2', 0.6)
+    STRUCTURE = _color('gray', 0.4)
+    DECORATION = _color('lightseagreen', 0.4)
+    ELECTRONIC = _color('mediumorchid', 0.5)
+
+    def __init__(self, color: Cq.Color):
+        self.color = color
+
 class Material(Enum):
+    """
+    A catalog of common material properties
+    """
 
     WOOD_BIRCH = 0.8, _color('bisque', 0.9)
     PLASTIC_PLA = 0.5, _color('azure3', 0.6)