There are a WIDE variety of casement
windows (crank windows). The Crank DonutTM works on a large, but specific, set of these windows. Your window must meet all of the following three conditions for the Crank DonutTM to function properly:

1) Your casement window must have a crank - some casement windows are outfitted with a 'butterfly' or other type of handle. You will have to reinstall a crank on any casement window that you want to lock open.

2) Your casement window must have a sill - there should be at least a 3" sill (from the face of the window frame to the edge of the sill). Most steel and aluminum casement windows, as well as wooden and vinyl bay windows, will meet this criteria. Many newer wooden and vinyl casement windows are installed such that there is effectively no sill, and the Crank DonutTM will not work on these casement windows.

3) The casement window operator (the box-like unit that the crank handle attaches to) must sit on the sill, or immediately above it - on most standard casement window installations the operator sits on, or almost on, the sill. On some remodels (due to window sizing), and in some casement window designs, the operator sits well above the sill. If the operator is more than 1/2" above the sill, the Crank DonutTM will not work. It is possible to place a permanent spacer or shim on the sill to effectively raise the sill height to the bottom of the operator.