▁is ▁for ▁error . ▁At ▁the ▁lower ▁levels , ▁the ▁designer ▁may ▁make ▁certain ▁elements ▁in ▁the ▁combination ▁slightly ▁lower , ▁to ▁make ▁it ▁easier . ▁F ence ▁height ▁also ▁has ▁some ▁influence ▁on ▁the ▁horse ' s ▁take - off ▁distance , ▁usually ▁decre asing ▁both ▁the ▁take - off ▁and ▁landing , ▁although ▁this ▁is ▁only ▁a ▁great ▁variant ▁when ▁the ▁f ences ▁are ▁ 4 ▁feet ▁ 6 ▁inches ▁or ▁higher . ▁ ▁Ter rain : ▁this ▁is ▁especially ▁a ▁factor ▁for ▁event ers ▁as ▁they ▁ride ▁combinations ▁cross - country . ▁A ▁combination ▁on ▁the ▁down hill ▁tends ▁to ▁length en ▁the ▁st ride , ▁and ▁on ▁the ▁u ph ill ▁it ▁tends ▁to ▁short en ▁it . ▁Go ing ▁through ▁water ▁tends ▁to ▁short en ▁the ▁st ride . ▁Land ing ▁up ▁a ▁bank ▁causes ▁a ▁shorter ▁landing ▁distance ▁than ▁from ▁an ▁u pr ight ▁obst acle . ▁ ▁To ▁negoti ate ▁a ▁combination ▁successfully , ▁a ▁r ider ▁must ▁maintain ▁the ▁qual ities ▁needed ▁in ▁all ▁r iding : ▁rh ythm , ▁balance , ▁and ▁imp ulsion ▁as ▁they ▁approach ▁the ▁f ence . ▁They ▁must ▁also ▁have ▁a ▁great ▁understanding ▁of ▁their ▁horse ' s ▁st ride ▁length , ▁so ▁that ▁they ▁may ▁know ▁how ▁much ▁they ▁need ▁to ▁short en ▁or ▁length en ▁it ▁for ▁each ▁particular ▁combination . ▁ ▁Before ▁r iding ▁the ▁course , ▁the ▁r ider ▁should ▁walk ▁the ▁distances ▁of ▁the ▁combination ▁and ▁decide ▁the ▁st ride ▁from ▁which ▁they ▁should