Example #R2eboot Device Constructed By Me

All parts are mounted on the board and partly connected to each other.
On the lower right corner you see the diodes used for combining power from three signal inputs. They are directly connected to the plug.
In the middle the 74HCT688 can be found. It's the only place where it will fit inside the plug covers.
The space in the top left corner is used up by the negator circuit. Underneath it switching transistor and control LED fill the last bit on this side.

To make wiring as transparent as possible, wires carrying the signal to compare are mounted on top of the board. Plug's D0-D7 is on this site too.
If you use thinner wires you might get around squezzing them like in the picture.
Both transistors are now bend over thus reducing height and allowing the cover to close properly.

All ground pins are short circuited on the plug to avoid hazzles with cables and/or plugs that dont connect all of them. Later on there is going to be plenty of solder since the ground connection also keeps plug and board together. (After reset cord has been attached.)
Most of the connections on this side go from ground or Vcc to the IC and define what bit combination or value sent to the parallel port will later on trigger the reset.

Fully assembled and equipped with a long cord. Inside the cord itself is heavily soldered to ground pins to prevent accidential pulls from rip it off - or worse - damage the device itself.
This is necessary because the plug's built in strain relief had to be removed to give enough room for the IC.
Black rubber covers poor drilling and improves LED visibility a little bit. If you find your parallel port powerful enough you can use stronger LEDs. But standard is 5mA each pin and there are other things to be supplied with energy besides the LED.