The 'phonograms' introduce the nonphonetic aspects of English. The Double Sandpaper Letters form the first stage of the Complete Reading Scheme #0.055.00.
Included in the set of 16 double letter combinations are: er, ee, ar, ou, oo, ai, or, ue, ie, au, oa, sh, ch, oy, th, qu. The double sandpaper letters are on boards painted green.
Boards are 24x12cm and 26x19cm and 22x12cm.