The phrase "lace curtains" refers to finely woven curtains made of delicate lace fabric. This term is often used metaphorically to describe an attempt to hide or mask something, like secretive behavior or a pretentious front. Full definition
I used to have lace curtains in a previous home at my kitchen window that faced the driveway. (lovegrowswild.com)
Each team was given a balloon to simulate a belly, some ribbon, pretty fabric, toilet paper, and an old lace curtain to create their shirt. (thefrugalgirls.com)
The sheer or lace curtains blowing in the summer breezes is so romantic! (theinspiredroom.net)