diff --git a/masque/file/dxf.py b/masque/file/dxf.py
index 0f0b753..335cd80 100644
--- a/masque/file/dxf.py
+++ b/masque/file/dxf.py
@@ -59,8 +59,8 @@ def write(pattern: Pattern,
      array with rotated instances must be manhattan _after_ having a compensating rotation applied.
 
     Args:
-        patterns: A Pattern or list of patterns to write to file.
-        file: Filename or stream object to write to.
+        patterns: A Pattern or list of patterns to write to the stream.
+        stream: Stream object to write to.
         modify_original: If `True`, the original pattern is modified as part of the writing
             process. Otherwise, a copy is made and `deepunlock()`-ed.
             Default `False`.
diff --git a/masque/file/gdsii.py b/masque/file/gdsii.py
index a1f0877..98a9a51 100644
--- a/masque/file/gdsii.py
+++ b/masque/file/gdsii.py
@@ -1,5 +1,15 @@
 """
 GDSII file format readers and writers
+
+Note that GDSII references follow the same convention as `masque`,
+  with this order of operations:
+   1. Mirroring
+   2. Rotation
+   3. Scaling
+   4. Offset and array expansion (no mirroring/rotation/scaling applied to offsets)
+
+  Scaling, rotation, and mirroring apply to individual instances, not grid
+   vectors or offsets.
 """
 from typing import List, Any, Dict, Tuple, Callable, Union, Sequence, Iterable, Optional
 import re
@@ -23,7 +33,6 @@ from ..shapes import Polygon, Path
 from ..utils import rotation_matrix_2d, get_bit, set_bit, vector2, is_scalar, layer_t
 from ..utils import remove_colinear_vertices, normalize_mirror
 
-#TODO document how GDS rotation / mirror works
 #TODO absolute positioning
 
 
@@ -65,8 +74,8 @@ def write(patterns: Union[Pattern, List[Pattern]],
      prior to calling this function.
 
     Args:
-        patterns: A Pattern or list of patterns to write to file.
-        file: Filename or stream object to write to.
+        patterns: A Pattern or list of patterns to write to the stream.
+        stream: Stream object to write to.
         meters_per_unit: Written into the GDSII file, meters per (database) length unit.
             All distances are assumed to be an integer multiple of this unit, and are stored as such.
         logical_units_per_unit: Written into the GDSII file. Allows the GDSII to specify a
diff --git a/masque/repetition.py b/masque/repetition.py
index e1297d2..96c9214 100644
--- a/masque/repetition.py
+++ b/masque/repetition.py
@@ -22,6 +22,22 @@ class GridRepetition:
     """
     GridRepetition provides support for efficiently embedding multiple copies of a `Pattern`
      into another `Pattern` at regularly-spaced offsets.
+
+    Note that rotation, scaling, and mirroring are applied to individual instances of the
+     pattern, not to the grid vectors.
+
+    The order of operations is
+        1. A single refernce instance to the target pattern is mirrored
+        2. The single instance is rotated.
+        3. The instance is scaled by the scaling factor.
+        4. The instance is shifted by the provided offset
+            (no mirroring/scaling/rotation is applied to the offset).
+        5. Additional copies of the instance will appear at coordinates specified by
+            `(offset + aa * a_vector + bb * b_vector)`, with `aa in range(0, a_count)`
+            and `bb in range(0, b_count)`. All instance locations remain unaffected by
+            mirroring/scaling/rotation, though each instance's data will be transformed
+            relative to the instance's location (i.e. relative to the contained pattern's
+            (0, 0) point).
     """
     __slots__ = ('_pattern',
                  '_offset',
@@ -43,7 +59,7 @@ class GridRepetition:
     """ (x, y) offset for the base instance """
 
     _dose: float
-    """ Dose factor """
+    """ Scaling factor applied to the dose """
 
     _rotation: float
     """ Rotation of the individual instances in the grid (not the grid vectors).
@@ -76,7 +92,7 @@ class GridRepetition:
     """ Number of instances along the direction specified by the `b_vector` """
 
     identifier: Tuple[Any, ...]
-    """ Arbitrary identifier """
+    """ Arbitrary identifier, used internally by some `masque` functions. """
 
     locked: bool
     """ If `True`, disallows changes to the GridRepetition """
@@ -96,15 +112,23 @@ class GridRepetition:
                  identifier: Tuple[Any, ...] = ()):
         """
         Args:
+            pattern: Pattern to reference.
             a_vector: First lattice vector, of the form `[x, y]`.
-                Specifies center-to-center spacing between adjacent elements.
+                Specifies center-to-center spacing between adjacent instances.
             a_count: Number of elements in the a_vector direction.
             b_vector: Second lattice vector, of the form `[x, y]`.
-                Specifies center-to-center spacing between adjacent elements.
+                Specifies center-to-center spacing between adjacent instances.
                 Can be omitted when specifying a 1D array.
             b_count: Number of elements in the `b_vector` direction.
                 Should be omitted if `b_vector` was omitted.
+            offset: (x, y) offset applied to all instances.
+            rotation: Rotation (radians, counterclockwise) applied to each instance.
+                       Relative to each instance's (0, 0).
+            mirrored: Whether to mirror individual instances across the x and y axes.
+            dose: Scaling factor applied to the dose.
+            scale: Scaling factor applied to the instances' geometry.
             locked: Whether the `GridRepetition` is locked after initialization.
+            identifier: Arbitrary tuple, used internally by some `masque` functions.
 
         Raises:
             PatternError if `b_*` inputs conflict with each other
diff --git a/masque/subpattern.py b/masque/subpattern.py
index 7f4bb87..f0af4c0 100644
--- a/masque/subpattern.py
+++ b/masque/subpattern.py
@@ -2,6 +2,7 @@
  SubPattern provides basic support for nesting Pattern objects within each other, by adding
   offset, rotation, scaling, and other such properties to the reference.
 """
+#TODO more top-level documentation
 
 from typing import Union, List, Dict, Tuple, Optional, Sequence, TYPE_CHECKING, Any
 import copy
@@ -51,13 +52,11 @@ class SubPattern:
     """ Whether to mirror the instanc across the x and/or y axes. """
 
     identifier: Tuple[Any, ...]
-    """ An arbitrary identifier """
+    """ Arbitrary identifier, used internally by some `masque` functions. """
 
     locked: bool
     """ If `True`, disallows changes to the GridRepetition """
 
-
-    #TODO more documentation?
     def __init__(self,
                  pattern: Optional['Pattern'],
                  offset: vector2 = (0.0, 0.0),
@@ -67,6 +66,17 @@ class SubPattern:
                  scale: float = 1.0,
                  locked: bool = False,
                  identifier: Tuple[Any, ...] = ()):
+        """
+        Args:
+            pattern: Pattern to reference.
+            offset: (x, y) offset applied to the referenced pattern. Not affected by rotation etc.
+            rotation: Rotation (radians, counterclockwise) relative to the referenced pattern's (0, 0).
+            mirrored: Whether to mirror the referenced pattern across its x and y axes.
+            dose: Scaling factor applied to the dose.
+            scale: Scaling factor applied to the pattern's geometry.
+            locked: Whether the `SubPattern` is locked after initialization.
+            identifier: Arbitrary tuple, used internally by some `masque` functions.
+        """
         object.__setattr__(self, 'locked', False)
         self.identifier = identifier
         self.pattern = pattern