Question about Ohmex Air cooler COL-9090PRO

There is a drawer in the back that can be easily removed (You remove the filter from the plastics container and then you wash it). In anycase the cooler did the job, but it is not an air conditioner of course.

When I pull out the water drawer, there is a block inside that is firmly attached to the bottom of the drawer, and I can't unscrew it to completely remove the drawer.... Is there a photo of where and how to press to unfasten the mechanism that is attached to the bottom of the water drawer