A blind roll-up system comprising: hingedly connected slats (2) having a groove between adjacent slats; a roll-up drum (6), with ribs (10) for insertion in the grooves, thereby to move the slats (2) and associated with first drive means, such as a first pulley (12); two pairs of guides (46, 48) for unrolling the slats on different sides of the drum (6); a semi-cylindrical shell (14) which may be locked in a position allowing said double unrolling; a clutch member (34) which alternately locks the pulley (12) with the shell (14) or leaves it free.

When the shell (14) is locked in place and the first drive means are declutched, the blind may unroll along the guides (48) and thus show to the inside, making it accessible for cleaning, the side normally facing outwardly.