To open the hole blocked by solder, heat the solder pad with the tip of a soldering iron. Push through the molten solder from the other side with a staple or sewing needle.

In our case, we decided to use a right angle pick. Lead solder will not stick to steel, so pretty much any thin steel can be used.

Pushing the tool all the way through the hole may require heating the pad several times. As a rule of thumb, heat the solder just enough for it to melt, then remove the soldering tip from the pad. Excessive heat will damage electronic components.