Double Letters

tav	resh	peh	kaf	dalet	gimel	bet	Dagesh
תּ	רּ	פּףּ	כּךּ	דּ	גּ	בּ	With
T	R	P	K	D	G	B	With

Th/S	-	Ph (F)	Kh	Dh	-	V	Without
ת	ר	פף	כך	ד	ג	ב	Without
/θ/ or /s/		/f/	/χ/	/ð/			Without

To remember these letters, say: BiG'Dei KaPoReTh (בִּגְדֵי־כַּפֹּרֶת.) This means “covering of the mercy seat”