This bracket holds a dual compact flash to IDE adapter in a Microchannel slot. The dual slot board is seen by the PC as two drives (primary and secondary). When using two drives it should be installed on the end of the IDE cable. When the jumper is on pins 1 and 2 the top card slot is the master and the bottom card is the slave. When the jumper is on pins 2 and 3 the top card is the slave and the bottom card is the master. No other device can be on the IDE cable when using two CF cards (as the card it seen as two IDE devices). If you only want to use one CF card you can move the card to the secondary IDE port on the cable and use the top slot. The jumper should be on pins 2 and 3.