STRUCTURE,comprising: a body comprising at least first and second perforated fluid flow holes that meet each other at an intersection within the body; a pig routing insert (1, 5, 20, 21) positioned at the intersection in the body, the pig routing insert comprising: an insert body; a substantially unrestricted flow opening (3C, 5A) extending through the insert body, the substantially unrestricted flow opening (3C, 5A) being in uninterrupted communication with the first perforated fluid flow hole so as to allow the substantially unrestricted fluid flow from the first perforated fluid flow hole through the substantially unrestricted flow opening (3C, 5A); and a partially restricted flow opening (3A, 5F) defined in the insert body comprising at least one pig blocking structure positioned within the partially restricted flow opening (3A, 5F), wherein the partially restricted flow opening (3A, 5F) is in uninterrupted communication with the second perforated fluid flow hole to allow substantially unrestricted fluid flow from the second perforated fluid flow hole through the partially restricted flow opening (3A, 5F) whilst blocking the passage of a cleaning pig through the partially restricted flow opening (3A, 5F); characterized in that: a first lining is formed on an inner surface of the first perforated fluid flow hole; and a second lining is formed on an inner surface of the second perforated fluid flow hole. a body comprising at least first and second perforated fluid flow holes that meet each other at an intersection within the body; a pig routing insert (1, 5, 20, 21) positioned at the intersection in the body, the pig routing insert comprising: an insert body; a substantially unrestricted flow opening (3C, 5A) extending through the insert body, the substantially unrestricted flow opening (3C, 5A) being in uninterrupted communication with the first perforated fluid flow hole so as to allow the substantially unrestricted fluid flow from the first perforated fluid flow hole through the substantially unrestricted flow opening (3C, 5A); and a partially restricted flow opening (3A, 5F) defined in the insert body comprising at least one pig blocking structure positioned within the partially restricted flow opening (3A, 5F), wherein the partially restricted flow opening (3A, 5F) is in uninterrupted communication with the second perforated fluid flow hole to allow substantially unrestricted fluid flow from the second perforated fluid flow hole through the partially restricted flow opening (3A, 5F) whilst blocking the passage of a cleaning pig through the partially restricted flow opening (3A, 5F); characterized in that: a first lining is formed on an inner surface of the first perforated fluid flow hole; and a second lining is formed on an inner surface of the second perforated fluid flow hole. an insert body; a substantially unrestricted flow opening (3C, 5A) extending through the insert body, the substantially unrestricted flow opening (3C, 5A) being in uninterrupted communication with the first perforated fluid flow hole so as to allow the substantially unrestricted fluid flow from the first perforated fluid flow hole through the substantially unrestricted flow opening (3C, 5A); and a partially restricted flow opening (3A, 5F) defined in the insert body comprising at least one pig blocking structure positioned within the partially restricted flow opening (3A, 5F), wherein the partially restricted flow opening (3A, 5F) is in uninterrupted communication with the second perforated fluid flow hole to allow substantially unrestricted fluid flow from the second perforated fluid flow hole through the partially restricted flow opening (3A, 5F) whilst blocking the passage of a cleaning pig through the partially restricted flow opening (3A, 5F); characterized in that: a first lining is formed on an inner surface of the first perforated fluid flow hole; and a second lining is formed on an inner surface of the second perforated fluid flow hole. a first lining is formed on an inner surface of the first perforated fluid flow hole; and a second lining is formed on an inner surface of the second perforated fluid flow hole.