▁is ▁kept ▁cli pped ▁in ▁cold ▁weather , ▁the ▁blank et ▁cannot ▁be ▁taken ▁off ▁until ▁war mer ▁weather ▁arriv es ▁in ▁the ▁spring . ▁ ▁If ▁a ▁horse ▁is ▁subject ed ▁to ▁cold ▁weather ▁without ▁either ▁a ▁blank et ▁or ▁a ▁natural ▁hair ▁coat ▁to ▁keep ▁it ▁warm , ▁it ▁may ▁become ▁ill , ▁and ▁vulner able ▁to ▁sick ness es ▁such ▁as ▁influen za . ▁ ▁He avy ▁blank ets ▁for ▁warm th ▁make ▁up ▁the ▁bulk ▁of ▁the ▁horse ▁blank et ▁market , ▁but ▁light weight ▁blank ets ▁may ▁be ▁used ▁in ▁the ▁summer ▁to ▁help ▁the ▁animal ▁w ard ▁off ▁f lies ▁and ▁to ▁prevent ▁the ▁hair ▁coat ▁from ▁ble aching ▁out . ▁ ▁Such ▁blank ets ▁are ▁usually ▁called ▁a ▁" sheet " ▁or ▁a ▁" fly ▁sheet ". ▁They ▁are ▁usually ▁made ▁of ▁some ▁type ▁of ▁n yl on ▁or ▁strong ▁synth etic ▁fi ber , ▁but ▁with ▁the ▁capacity ▁to ▁" bre at he " ▁so ▁that ▁the ▁animal ▁remains ▁cool . ▁ ▁Most ▁have ▁a ▁smooth ▁n yl on ▁l ining ▁in ▁front ▁to ▁prevent ▁hair ▁from ▁we aring ▁off ▁on ▁the ▁shoulders . ▁ ▁They ▁are ▁becoming ▁increasing ly ▁popular , ▁particularly ▁with ▁the ▁rise ▁of ▁insect ▁bor ne ▁dise ases ▁such ▁as ▁West ▁N ile ▁fe ver . ▁ ▁Any ▁blank et ▁may ▁be ▁supp lement ed ▁with ▁a ▁neck ▁cover ▁or ▁a ▁full ▁h ood . ▁ ▁Ne ck ▁covers ▁are ▁often ▁attached ▁directly ▁to ▁the ▁blank et . ▁ ▁H ood