Screen device for a screen rollable onto and unrollable from a screen roller, comprising a frame with a protective case and at least one lateral guide (3, 4); and a screen roller and a screen rollable onto and unrollable from said screen roller and attached on one of its sides to the screen roller, said lateral guide comprising: a frame profile (10, 10') that extends in a longitudinal direction from the lower side of the protective case and at least one screen profile (20, 20', 30, 30') that extends in the longitudinal direction from the lower side of the protective case; and an installation state when the frame profile is detached from the at least one screen profile and a working state when at least one screen profile is connected to the frame profile, wherein the frame profile has a breadth (b) that corresponds to the breadth (b') of the lower side of the protective case; and, in the installation state, an installation passage for allowing passage of the lateral side of the screen roller in the longitudinal direction, and wherein the lateral guide in the working state has a screen profile passage for allowing passage of the lateral side of the screen, characterised in that in the installation state the lateral guide has at least one access opening for the orthogonal transverse insertion or removal of the lateral sides of the screen roller in the installation passage in transverse directions, the transverse directions encompassing the orthogonal transverse direction and depth direction transverse to the longitudinal direction and that, in the working state, the part of the frame profile bordering the installation passage and at least one screen profile together form a mainly rectangular profile. for a screen rollable onto and unrollable from a screen roller, comprising a frame with a protective case and at least one lateral guide (3, 4); and a screen roller and a screen rollable onto and unrollable from said screen roller and attached on one of its sides to the screen roller, said lateral guide comprising: a frame profile (10, 10') that extends in a longitudinal direction from the lower side of the protective case and at least one screen profile (20, 20', 30, 30') that extends in the longitudinal direction from the lower side of the protective case; and an installation state when the frame profile is detached from the at least one screen profile and a working state when at least one screen profile is connected to the frame profile, wherein the frame profile has a breadth (b) that corresponds to the breadth (b') of the lower side of the protective case; and, in the installation state, an installation passage for allowing passage of the lateral side of the screen roller in the longitudinal direction, and a frame profile (10, 10') that extends in a longitudinal direction from the lower side of the protective case and at least one screen profile (20, 20', 30, 30') that extends in the longitudinal direction from the lower side of the protective case; and an installation state when the frame profile is detached from the at least one screen profile and a working state when at least one screen profile is connected to the frame profile, wherein the frame profile has a breadth (b) that corresponds to the breadth (b') of the lower side of the protective case; and, in the installation state, an installation passage for allowing passage of the lateral side of the screen roller in the longitudinal direction, and wherein the lateral guide in the working state has a screen profile passage for allowing passage of the lateral side of the screen, characterised in that in the installation state the lateral guide has at least one access opening for the orthogonal transverse insertion or removal of the lateral sides of the screen roller in the installation passage in transverse directions, the transverse directions encompassing the orthogonal transverse direction and depth direction transverse to the longitudinal direction and that, in the working state, the part of the frame profile bordering the installation passage and at least one screen profile together form a mainly rectangular profile.