I asked my boyfriend to assemble a chair. Watching him handle the power drill so smoothly was so sexy that I kept teasing him—until he finally stopped working and glared at me. That’s when I noticed the grooves in the armrests and legs of the chair and wondered what they were for. The moment he finished, he ordered me to sit down in a firm tone and pulled out a set of cuffs. That’s when I realized what those grooves were for.