The most distinctive type of Batak manuscripts from north Sumatra are the pustaha, folded concertina-style books written on treebark, which mostly contain notes on divination and magical formulae. Pustaha can vary considerably in length and size – those in the British Library collection range from the relatively large, with pages each 28 x 20 cm (Add 19378) to the tiny, measuring only 4.5 x 3 cm (such as MSS Batak 9). Simpler manuscripts may not have any special covers, ending just with the final leaves of treebark, but quite a few Batak pustaha have covers of wood. Sometimes these are finely carved, particularly on the front cover, but occasionally also on the back. Manuscripts may also have a plaited band made of split rattan or bamboo, which can be placed around the covers of the manuscript to clasp the book closed. Additionally, there may be two holes drilled into the top wooden cover for a string of ijuk fronds to be attached so that the manuscript could be carried or hung easily.