▁with ▁an ▁invert ed ▁triangle ▁of ▁logs ▁pointing ▁down wards , ▁res emb ling ▁a ▁sh ark ' s ▁top ▁j aw . ▁ ▁Sk in ny ▁ ▁A ▁" sk in ny " ▁is ▁any ▁f ence ▁with ▁a ▁narrow ▁face . ▁These ▁require ▁accurate ▁r iding ▁and ▁the ▁ability ▁to ▁keep ▁the ▁horse ▁straight , ▁as ▁it ▁is ▁easy ▁for ▁a ▁horse ▁to ▁" gl ance ▁off " ▁such ▁narrow ▁obst acles . ▁Com bin ations ▁involving ▁sk inn ies ▁become ▁increasing ly ▁common ▁as ▁the ▁r ider ▁moves ▁up ▁the ▁levels ▁because ▁they ▁reduce ▁the ▁degree ▁of ▁error ▁that ▁is ▁available ▁if ▁the ▁r ider ▁is ▁to ▁successfully ▁negoti ate ▁the ▁f ence . ▁ ▁Stone ▁Wall ▁These ▁j umps ▁are ▁solid ▁walls ▁made ▁out ▁of ▁stone ▁or ▁a ▁similar ▁material . ▁ ▁They ▁sometimes ▁have ▁logs ▁placed ▁on ▁top ▁to ▁make ▁them ▁larger ▁or ▁change ▁the ▁appearance . ▁ ▁Sun ken ▁road ▁ ▁These ▁are ▁combination ▁j umps ▁involving ▁banks ▁and ▁rails . ▁ ▁At ▁the ▁lower ▁levels , ▁it ▁may ▁consist ▁of ▁a ▁bank ▁down , ▁with ▁a ▁few ▁str ides ▁to ▁a ▁bank ▁up . ▁At ▁the ▁upper ▁levels , ▁the ▁sun ken ▁road ▁often ▁is ▁quite ▁complicated , ▁usually ▁beginning ▁with ▁a ▁set ▁of ▁rails , ▁with ▁either ▁one ▁st ride ▁or ▁a ▁b ounce ▁distance ▁before ▁the ▁bank ▁down , ▁a ▁st ride ▁in ▁the ▁" bottom " ▁of ▁the ▁road ▁before ▁jump ing ▁the ▁bank ▁up , ▁and ▁another ▁st ride ▁or ▁b ounce