Is it really meant to be sealed?

I bought these lids to cover saucepans Ingenio (Lot "Texting" in 16cm and 18cm) and they do not adapt to it. On the one hand they are not supposed to be placed on hot surfaces so it must wait until the dish has cooled to encompass this. Moreover, it is almost impossible to return the vertical tab into the pan and then close the cover to make it airtight. We use the larger lid to cover the pot with the tongue out.