Stocks ?

Hi guys,

What could be the best guess for the meaning of "stocks" marked in red below?

Thanks for your help.
pb

----------

The resort has 70 marked downhill runs (mainly red and blue with a few black and green) totalling over 80km, a dedicated snowboarding area and some cross-country routes. Some runs start almost at the top of Veleta, the Sierra Nevada’s second-highest peak. A one-day ski pass plus rental of skis, boots and stocks or snowboard costs €50 to €60 depending when you go. The resort has several ski and snowboard schools: six hours’ skiing instruction in group classes costs €63. Nonskiers can ride cable cars up