If you've just ordered work pants from an online retailer (after seeing "work pants for sale online") because you ripped your current pair or pairs, you should still attempt to patch up your old pants at least temporarily. Mail can be delayed or lost, and while companies are generally good about sending replacement shipments out quickly, you don't want to spend the next few days or weeks with ripped pants. Patching them can be rather simple, but you do have to ensure you use the right materials.
Iron-on patches seem like the most obvious, easiest option, but in many cases, the patches aren't meant to be washed. Or if they are, you get maybe a few washes before the patch falls off. While the material used to adhere the patch to the clothing seems secure after you've ironed it on and let it cool, it isn't always water-resistant. If your new pants are delayed, you could end up having to iron on new patches every time you do laundry.
Double-check the labels before you grab a pack of iron-on patches off the shelf in the store. The instructions should say whether you can wash the patch or not -- but be prepared to find only non-washable patches.
To tack something in sewing means to make very quick stitches meant to hold something in place temporarily. You usually hear this term associated with hemming pant legs very quickly. Tacking is better than using non-washable iron-on patches for casual clothing because the stitches will hold up in the wash. However, it will look "patchy," of course. You will need a piece of material that matches your pants, or at least something that won't make you feel self-conscious.
All you have to do is thread a needle and knot the ends of the thread, and then make several quick stitches around the patch and clothing. Don't worry about making the stitches perfect -- you just want to connect the two pieces. Trim the edges of the patch to make it look neat.
Fusible web is a heat-sensitive strip of material that fuses materials together. In other words, if you place the fusible web between the patch and pants and heat the web, such as through ironing, the web will fuse the two pieces together. As with iron-on patches, you'll have to check to see that the web can withstand washing, but it usually can.
Trim the patch to be wider than the hole or tear by a little more than the width of the fusible web. Place the web around the tear or hole and place the patch on top. Iron according to the package instructions.
When you do get your new pants and have checked that they fit, wash and cut up your old pants so that you have patch material at the ready should you need it. That lets you mend rips quickly while waiting for yet more shipments of clothing to arrive.