The vinyl curtains that cover the opening of the nest box give the hens a sense of a safe "nesting" area where they can lay their eggs.  Our curtains have a V-shaped opening cut in them to allow easy access to the laying area by the hens, but still allows the curtains to be large enough to block a signficant amount of light and provide that inviting nesting space to the hens.Some folks feel the V-shaped opening inhibits the hens from using the nest box when the nest box is first introduced to the hens and they are learning to use it.  If your hens are having trouble acclimating to the nest box, you can temporarily tape one (or use a manget) of the curtains to the roof to create a larger opening.  However, it has been our experience and working with customers who have had flocks with problems getting used to their new nest box that the issue is always something other than the curtains.  See our training tips for more info.Ultimately, we feel the V-shaped opening is a good balance between accessibility and the sense of sense of safety and security for the hens.