Cover for a wall vent to prevent insects and critters going in.

Load both STL files together into slicer so that they are aligned. Set the “_vent” STL to have no top/bottom layers and a relatively dense 2D infill. See the screen shot in the pictures. The “_frame” STL should have a few top and bottom layers as per usual

If used outdoors, then recommend that you use an appropriate filament such as ASA or PETG.