400 Watt Oil-Filled Dummy Load by N4SPP
A dummy load is just one of those standard tools that you need in the shack. It's a load that has a purely resistive impedance of 50 ohms at all frequencies of interest (HF in my case). You don't need to pollute the airwaves while just tuning or testing your transmitter!
https://www.nonstopsystems.com/radio/frank_radio_antenna_dummy.htm

Building A RF Dummy Load by VO1PWF
If your doing any home brewing gear for ham radio its a great idea to have a dummy load. This will to your radio be the perfect antenna...it will never radiate but your radio sees a perfect 50 Ohm impedance.
http://www.linuxwolfpack.com/dummyload-homebrew.php

Dummy load with a 50 Ω stripline (hybrid) resistor. by PAØFRI
Making a dummy load working well into the UHF region is pretty straightforward if one can obtain a 'stripline' or 'hybrid' resistor.
https://pa0fri.home.xs4all.nl/Diversen/Dummyl/dummyloadeng.htm

Oil Filled Dummy Load by AI4JI
This dummy load uses twenty non-inductive resistors in parallel to achieve fifty ohms over a very wide frequency range. The internal components are specially arranged and submerged in oil to dissipate heat and allow extended operation for transmitter tuning, testing and alignments.
https://www.nonstopsystems.com/radio/pdf-ant/antenna-dummy-article-1.pdf

QRP Dummy Load by N5ESE
This is another variation on the "parallel resistor" dummy load. This is one I built during my infatuation with copper pipe. It's perfect for QRP HF operation of 5-watts or less average power, and should be adequate for continuous operation at that level. It's light and compact, about 2-1/2" in length overall.
https://www.nonstopsystems.com/radio/pdf-ant/antenna-dummy-article-3.pdf

QRP Dummy Load and Power Detector by KB9II
Here's a simple but useful accessory for QRP operation: a dummy load - power meter. It presents a good 50-ohm 4-watt load for a transmitter while the rf detector circuit will let you measure the power into it.
http://my.core.com/~jematz/qrp/kb9ii-s3.htm