Yes, there has to be a valve depressor built into the gauge. As someone who made these for a number of years, getting the distance from the seal lip to the depressor dialed was a challenge, because the distance varied within a band maker to maker. If the distance isn't right, either there's air loss when the valve depresses early, or you have to really lean on it to get the valve depressor engaged. I solved it with a bushing and support that had some room to accordion, but it was a tough tolerance to hold consistently.