▁rich est ▁in ▁England ▁during ▁the ▁ 1 1 th ▁Century . ▁ ▁References ▁ ▁External ▁links ▁▁▁ ▁Category : Med ieval ▁English ▁sain ts ▁Category : 9 th - century ▁Christian ▁sain ts ▁Category : E ast ▁Ang li an ▁sain ts ▁Category : English ▁Christian ▁mon ks ▁Category : English ▁herm its ▁Category : 9 th - century ▁Christian ▁mon ks ▁Category : 9 th - century ▁English ▁people <0x0A> </s> ▁A ▁tra iler ▁tail , ▁boat ▁tail , ▁or ▁rear ▁fair ing ▁is ▁an ▁aer od ynamic ▁device ▁intended ▁to ▁improve ▁the ▁fuel ▁economy ▁of ▁semi - tra iler ▁tr uck s . ▁It ▁compr ises ▁a ▁set ▁of ▁pan els , ▁usually ▁col laps ible , ▁which ▁fol d ▁out ▁from ▁the ▁rear ▁of ▁the ▁tra iler , ▁creating ▁a ▁t aper ed ▁shape ▁that ▁reduces ▁drag ▁from ▁the ▁low - press ure ▁w ake ▁created ▁behind ▁the ▁tra iler . ▁Tra iler ▁t ails ▁are ▁one ▁form ▁of ▁aer od ynamic ▁technology ▁verified ▁by ▁the ▁U . S . ▁Environment al ▁Prote ction ▁Agency ' s ▁Sm art W ay ▁Transport ▁Part ners hip . ▁Tra iler ▁t ails ▁alone ▁have ▁demonstrated ▁a ▁fuel ▁sav ings ▁of ▁ 1 % – 5 %, ▁and ▁in ▁concert ▁with ▁tra iler ▁sk ir ts , ▁ 9 % ▁improvement ▁has ▁been ▁demonstrated . ▁ ▁Tra iler T ail ▁is ▁a ▁registered ▁tra dem ark ▁of ▁S TE M CO . ▁ ▁Super T ruck ▁project ▁At ▁least ▁one ▁model ▁of