Inspiration: These grates ensure that when we undertake underground travel (subway), we can breathe! As a result, they are plentiful and in this city, one cannot escape walking on them - especially when walking in a group. I confess to suffering a bit of agita when walking over these things. Not so much because I am worried about losing a heel (I tippytoe over them) but more because I am not convinced that they are entirely secure. I always feel like I am going to fall in!