A sideform (10) for a sideform system includes an elongate body member (12) defining a side forming face (14) and an opposed mounting portion (16) for mounting the body member on a sideform holder. At least one recessed region (18, 20), in which an insert is receivable, is defined in the body member (12). An engaging arrangement (22) is associated with the recessed region (18, 20) for securing the insert in position in the recessed region (18, 20). At least one attaching formation (28) is arranged on the body member (12) in association with the side forming face (14) for attaching an edge form.