Step-by-step instructions:
Step 1.
First of all, register a free FlexiHub account to be able to log into the app and connect to the remote devices associated with the account.
Note: you can register an account later in the app or if you already have a FlexiHub account, skip this step.
Step 2.
Choose a required number of connections and sign up for a FlexiHub trial.
Step 3.
Download and install the latest version of the app to all the machines that will use the same keyboard and mouse.
Step 4.
The final step would be logging into the app using your credentials.
The app will display a list of devices available for connection. Here you may press "Lock" button for devices you would like to keep blocked from the remote access. 
That’s it, your keyboard can now be used on all machines where FlexiHub is installed.
An ideal alternative to FlexiHub would be USB Network Gate, which offers a support for USB redirection to RDP session on top of regular access to remote USB devices. The software is compatible with the same platforms (Windows, macOS, Linux) and is able to function in a local network without the access to the Internet.
For Mac
FlexiHub does provide a support for macOS as well. Download and install it on all your machines that require a shared access to the keyboard and mouse.
Note: If some of your machines run Linux, download the app’s versions for it here
Pros and cons of the software method
Pros
- It only requires a couple of clicks to connect a device
- No need in additional hardware
- All apps have complete trial versions
- You can share not only keyboards and mice but any USB devices
Cons
- To make use of extra features you need to acquire a full version
- A shared device can only be accessed on one machine at a time
Using KVM switch for keyboard and mouse splitting
KVM switch is a hardware device that enables working with multiple computers not connected over network, using a single monitor, a single keyboard and a single mice.
All it takes is just 2 steps - first plug a keyboard and a mouse you would like to share into the USB ports of this box-like device, then connect the switch with the computers. As simple as it gets.
In most cases the switches are equipped with buttons to toggle between USB ports and computers.
You can use KVM switches to share not only keyboards and mice, but other devices as well such as microphones and speakers. The switches work with both Windows and Mac machines.
Hardware method pros and cons
Pros
- The price of KVM switches is generally lower than of the specialized software license
- It requires only several steps to share devices
Cons
- The workspace is cluttered with additional wires
- Does not work if the computers are far away from each other
Specialized software for USB sharing on Windows
This requires computers to be connected over local network: one of them should be set as the master, and the others as the slaves. The keyboard and mouse should be connected to the master machine.
Input Director
Install Input Director and setup your master system first: choose how to switch between your multiple computers - either by a combination of hotkeys defined by you or by dragging the mouse cursor across edges just like in a dual monitor setup.
Next define network address and add machines to it. The software enables you to share a common clipboard area in the network, set it up in Global Preferences. 
For more details on how to use the software read here.
Synergy
This cross platform software tool is ideal if the computers in your network run different operating systems.
You can customize the mechanism of switching between computers too - either press a hotkey combination or drag a cursor across the borders. Switch time is also customizable, and you can share a common clipboard area. 
Mouse Without Borders
This app should be installed on all machines in the network. When you launch the app you’ll be asked to enter the Security Code and the name of the computer you would like to connect to. The software allows you to connect not more than 4 machines and lock all network computers in one go. 
Apart from shared clipboard area, the app offers you a possibility to drag and drop files from one machine to another. The highlight of this app is its sleek intuitive interface.
