A piece of soft fabric or rubber is placed behind the beads, keeping them in place while the users manipulate them.
ɐ pˈiːs ʌv sˈɔft fˈæbɹɪk ɔːɹ ɹˈʌbɚɹ ɪz plˈeɪst bᵻhˌaɪnd ðə bˈiːdz, kˈiːpɪŋ ðˌɛm ɪn plˈeɪs wˌaɪl ðə jˈuːzɚz mənˈɪpjʊlˌeɪt ðˌɛm.