sometimes it is useful to be able to draw within the boundaries of an object but have strokes made outside of the object masked [hidden] whilst actually drawing - particularly handy when freehand drawing/sketching I think

one way to do this:

- you have your object on layer 1

- make two new layers: layer 2 and 3

- copy and paste in place to layer 3 your object

- on layer 3: if it is a compound object such as a clipview you need to convert it to editable shape [to make it a simple group] then place a large rectangle behind, select both, and subtract shapes - you will now see the original object on layer 1 showing through

- draw on layer 2 - the 'mask' on layer 3 hides the strokes made outside of the boundary of the object on layer 1

- when you have finished, hide layer 3, cut and paste in place your new objects from layer 2 to layer 1 and [add to] clipview [ if you leave them on layer 2 you will promote the original object from layer 1 to layer 2 when you clipview]

it is not as much work as it might seem, and worth it if you need this sort of masking - say you want to see how something looks instantly as you go along, rather than keep toggling it in and out of clipview