Not often used, but handy all the same for gradual height changes. Note that in US terms it can also be called "half double treble crochet"
by oana's crochet channel
by Crochet For Baby
by Lovely Crochet by Yanina
by marinella marifu6a
by SweetRhapsody12
by GemFOXvideo
by Hectanooga1 - Crochet, Knitting,