The Prebid Floor price module enables you to set floor prices straight in the auction, overriding the values you have in your specific SSPs. This is a very useful tool as it opens up a lot of optimization across all of your revenue sources.
Please notice that if an SSP does not support the Prebid Floor price module, it will simply use the floor price you have set in that particular SSP.
The Floor prices can be set on the placement level in the HB Manager tool, so just navigate to the placement you would like to adjust in your Accounts/Publisher/Website and it looks like this:
The first option "Price Floor" enables the Floor price you have entered across all the SSPs you have running on that placement (that support the Floor price module), and the second option "Price floor currency" sets the currency you would like to use across the call.
Please notice that the Floor price module also works with Amazon TAM/UAM, if you are working with them in the HB Manager; even though they are strictly speaking not part of the Prebid auction.