diff --git a/xray/mask.py b/xray/mask.py
index 5f55e87..ea51c60 100644
--- a/xray/mask.py
+++ b/xray/mask.py
@@ -116,7 +116,7 @@ def makeMaskGui(img,snapRange=60):
       mask.addRectangle(c1[0],c1[1],c2[0],c2[1])
     plt.imshow(mask.getMatplotlibMask())
     plt.pause(0.01)
-  fname = input("Enter a valid filename (ext .edf or .npy) to save the mask")
+  fname = input("Enter a valid filename (ext .edf or .npy) if you want to save the mask (empty otherwise)")
   try:
     if fname != '':
       ext = os.path.splitext(fname)[1]
@@ -130,7 +130,24 @@ def makeMaskGui(img,snapRange=60):
   finally:
     return mask
     
-    
+def maskBorder(width,shape):
+  mask = np.zeros(shape,dtype=bool)
+  mask[ :width  ,   :     ] = True
+  mask[ -width: ,   :     ] = True
+  mask[    :    , :width  ] = True
+  mask[    :    , -width: ] = True
+  return mask
+
+def maskCenterLines(width,shape):
+  mask = np.zeros(shape,dtype=bool)
+  if isinstance(width,int): width = (width,width)
+  c0 = int(shape[0]/2)
+  c1 = int(shape[1]/2)
+  w0 = int(width[0]/2)
+  w1 = int(width[1]/2)
+  mask[ c0-w0:c0+w0  ,       :      ] = True
+  mask[     :        ,  c1-w1:c1+w1 ] = True
+  return mask
 
 
 if __name__ == "__main__":