diff --git a/masque/ports.py b/masque/ports.py
index 36c47c4..688ed7a 100644
--- a/masque/ports.py
+++ b/masque/ports.py
@@ -1,4 +1,4 @@
-from typing import Iterable, KeysView, ValuesView, overload, Self
+from typing import Iterable, KeysView, ValuesView, overload, Self, Mapping
 import warnings
 import traceback
 import logging
@@ -303,7 +303,48 @@ class PortList(metaclass=ABCMeta):
         """
         s_ports = self[map_in.keys()]
         o_ports = other[map_in.values()]
+        return self.find_ptransform(
+            s_ports=s_ports,
+            o_ports=o_ports,
+            map_in=map_in,
+            mirrored=mirrored,
+            set_rotation=set_rotation,
+            )
 
+    @staticmethod
+    def find_ptransform(            # TODO needs better name
+            s_ports: Mapping[str, Port],
+            o_ports: Mapping[str, Port],
+            map_in: dict[str, str],
+            *,
+            mirrored: tuple[bool, bool] = (False, False),
+            set_rotation: bool | None = None,
+            ) -> tuple[NDArray[numpy.float64], float, NDArray[numpy.float64]]:
+        """
+        Given two sets of ports (s_ports and o_ports) and a mapping `map_in`
+          specifying port connections, find the transform which will correctly
+          align the specified o_ports onto their respective s_ports.
+
+        Args:t
+            s_ports: A list of stationary ports
+            o_ports: A list of ports which are to be moved/mirrored.
+            map_in: dict of `{'s_port': 'o_port'}` mappings, specifying
+                port connections.
+            mirrored: Mirrors `o_ports` across the x or y axes prior to
+                connecting any ports.
+            set_rotation: If the necessary rotation cannot be determined from
+                the ports being connected (i.e. all pairs have at least one
+                port with `rotation=None`), `set_rotation` must be provided
+                to indicate how much `o_ports` should be rotated. Otherwise,
+                `set_rotation` must remain `None`.
+
+        Returns:
+            - The (x, y) translation (performed last)
+            - The rotation (radians, counterclockwise)
+            - The (x, y) pivot point for the rotation
+
+            The rotation should be performed before the translation.
+        """
         s_offsets = numpy.array([p.offset for p in s_ports.values()])
         o_offsets = numpy.array([p.offset for p in o_ports.values()])
         s_types = [p.ptype for p in s_ports.values()]