Spiders and Homebuilding

Who advises spiders on where to build webs/homes? Why do spiders build homes between ladder posts? Every day I am a homewrecker and it is not my fault. Why between boat engines and boat gunnels that with one turn pull their homes apart like a Medieval stretching torture machine? Why on doorway corners where a head of a human is sure to impale itself on their night's work! What happened to innate knowledge and memory?