Seal, in particular automatically lowerable floor seal for doors, having the following features: - the seal comprises a seal housing, - the seal comprises at least one sealing means, which is fitted preferably in the seal housing, - the seal comprises fastening means (3, 4, 5, 6, 7, 9, 10, 11) for fastening the seal housing in a groove of a door or of a window, - the fastening means (3, 4, 5, 6, 7, 9, 10, 11), prior to the seal being installed in the groove, are arranged on the seal housing in at least partially captive fashion, - at least one of the fastening means (7, 9, 10, 11) has one or more elements (71a, b; 91a, b; 112) for pressing onto and/or into the groove of the door or of the window, e.g. for clawed engagement thereon and/or therein, - the at least one fastening means (7, 9, 10, 11), which has the element or elements (71a, b; 91a, b; 112) for pressing-on or pressing-in purposes, has one or more spreading elements (74, 95, 111), which are suitable, and intended, for moving the elements (71a, b; 91a, b; 112) or the element (71a, b; 91a, b; 112) for pressing-on and/or pressing-in purposes from the first position into the second position and/or vice versa, characterized in that - the spreading element or elements (74, 95, 111) is or are suitable, and intended, for changing over from the first position to the second position and/or vice versa by a linear movement - without the use of any tools, on account of impact or of pressing action, or - using a tool, which comprises an impact means or a pressure-exerting means, on account of impact by way of the impact tool or pressing being exerted by way of the pressure-exerting tool. - the seal comprises a seal housing, - the seal comprises at least one sealing means, which is fitted preferably in the seal housing, - the seal comprises fastening means (3, 4, 5, 6, 7, 9, 10, 11) for fastening the seal housing in a groove of a door or of a window, - the fastening means (3, 4, 5, 6, 7, 9, 10, 11), prior to the seal being installed in the groove, are arranged on the seal housing in at least partially captive fashion, - at least one of the fastening means (7, 9, 10, 11) has one or more elements (71a, b; 91a, b; 112) for pressing onto and/or into the groove of the door or of the window, e.g. for clawed engagement thereon and/or therein, - the at least one fastening means (7, 9, 10, 11), which has the element or elements (71a, b; 91a, b; 112) for pressing-on or pressing-in purposes, has one or more spreading elements (74, 95, 111), which are suitable, and intended, for moving the elements (71a, b; 91a, b; 112) or the element (71a, b; 91a, b; 112) for pressing-on and/or pressing-in purposes from the first position into the second position and/or vice versa, - the spreading element or elements (74, 95, 111) is or are suitable, and intended, for changing over from the first position to the second position and/or vice versa by a linear movement - without the use of any tools, on account of impact or of pressing action, or - using a tool, which comprises an impact means or a pressure-exerting means, on account of impact by way of the impact tool or pressing being exerted by way of the pressure-exerting tool. - without the use of any tools, on account of impact or of pressing action, or - using a tool, which comprises an impact means or a pressure-exerting means, on account of impact by way of the impact tool or pressing being exerted by way of the pressure-exerting tool.