They have installed the new power supply card into the Space Telescope Imaging Spectrograph during the fourth spacewalk of the Hubble Repair Mission. The STIS had stopped working in 2004 due to power failures. To remove the cover plate of the STIS required unscrewing 111 fasteners, using a special capture unit to keep them from floating off. When the fasteners were installed, there was no expectation that they would ever be removed in space!
