diff --git a/cpdfchop.ml b/cpdfchop.ml
index cbd9703..8b9b0c9 100644
--- a/cpdfchop.ml
+++ b/cpdfchop.ml
@@ -1,12 +1,22 @@
 open Pdfutil
 open Cpdferror
 
-(* Prevent duplication of content by sharing content streams *)
-(* Resources - patterns etc. - pattern matrices *)
-(* Bookmarks: merge/duplicate them *)
-(* Annotations: merge/duplicate them *)
-(* Page boxes - mediabox or cropbox used? Output modifies all boxes? *)
-(* fast/slow *)
+(* Resources - what to do with each. Bookmarks? Annotations - must be duplicated... *)
+(* Test how the sharing affects other cpdf operations. *)
 
-(* Chop pages into pieces *)
-let chop ~x ~y pdf range = pdf
+(* Chop a single page into pieces. We prefer the cropbox when available. We set
+   mediabox only, and delete any other boxes. *)
+let chop_boxes x y p = [p; p]
+
+(* Chop pages in the range into pieces *)
+let chop ~x ~y pdf range =
+  let pages = Pdfpage.pages_of_pagetree pdf in
+  let pages =
+    flatten
+      (map2
+        (fun n p -> if mem n range then (chop_boxes x y p) else [p])
+        (ilist 1 (Pdfpage.endpage pdf))
+        pages)
+  in
+  let changes = [] in (* FIXME *)
+    Pdfpage.change_pages ~changes true pdf pages
diff --git a/cpdfcommand.ml b/cpdfcommand.ml
index 778ca84..e78692f 100644
--- a/cpdfcommand.ml
+++ b/cpdfcommand.ml
@@ -4379,7 +4379,9 @@ let go () =
       in
         Cpdfcomposition.show_composition filesize json pdf
   | Some (Chop (x, y)) ->
-      ()
+      let pdf = get_single_pdf args.op false in
+      let range = parse_pagespec_allow_empty pdf (get_pagespec ()) in
+        write_pdf false (Cpdfchop.chop ~x ~y pdf range)
 
 (* Advise the user if a combination of command line flags makes little sense,
 or error out if it make no sense at all. *)