Using a bain marie, melt the chocolate in bowl sitting over simmering water. (make sure that the water does not touch the bottom of the bowl filled with chocolate).
Line a baking sheet with parchment paper.
Once the chocolate is melted dip each of the pecans and the pretzels into the melted chocolate and then using a fork quickly remove and set on the parchment paper. You will have to work quickly in connecting the pretzels onto the pecan as you want the chocolate to dry in order to help them stick. The goals is to place them in a way that makes the pretzels look like spider legs and the pecan to be the spider body. You should place four spider legs per side of the pecan.
Set them in the fridge to cool and then set out on a platter.