The new alphabet stamp sets in the catalog are photopolymer and there is a nice advantage to using this type of stamp set for letters. As you can see on the block beside the cards below, you can line them all up on your block at one time and know they will be straight.
Of course, if you need a letter more than once, you would have to stamp a couple times, but lining the letters up is still not too difficult.
I added some images from Work of Art behind the photopolymer stamped image and used Pool Party, Coastal Cabana and Bermuda Bay for those.
Work of Art, Metro Type Alphabet
Stazon Black, Coastal Cabana, Pool Party, Bermuda Bay ink
Coastal Cabana, Whisper White and Bermuda Bay card stock