Expanding foam! For anyone looking to mend their fence post, install a birdfeeder or a mailbox, check out this easy (and DIY) method. 👍 Here we are using the Sika PostFix-a two-part, pre-proportioned polyurethane resin. When it is mixed (in the bag) it produces an expanding foam. You can find it at your local home improvement stores. Just make sure you use the proper protection-gloves, safety glasses. Here’s what to do: 👉Lay down the pkg and roll the bag so you break the seal. Mix it up by run