There exists a competition in which a speaker must deliver a presentation in front of a slide deck that advances automatically every few seconds. The biggest challenge is knowing when the slide will change. Because most of us are not capable of simultaneously counting time and speaking, these talks often feature either awkward pauses waiting for the next slide or a rush to finish talking about a slide that disappeared a few seconds ago.

Prior to such a competition, one of the speakers asked me how to create a bar that would display across the bottom and gradually disappear as time expired. Here is how to do this:

Step 1: Create your slide

In PowerPoint, create your slides as you like each slide and set them to advance automatically. Fig. 1 shows an example of such a slide.

Fig. 1

Step 2: Draw a rectangle

Select one of your slides and insert a short wide rectangle shape at the bottom. From the Insert ribbon, select Shapes and click the rectangle shape, as shown in Fig. 1; then, drag your mouse along the bottom of the slide to draw the rectangle, as shown in Fig. 2. Make the rectangle exactly as wide as the slide.

Fig. 2

Fig. 3

Step 3: Animate the rectangle

Select the rectangle shape you just added. From the Animations ribbon, expand the list of animations and select "Wipe" from the "Exit" section, as shown in Fig. 4.

Fig. 4

By default, the "Wipe" animation will wipe the shape from the bottom. You want to wipe it from the right. Select the shape and, from the Animations ribbon, select Effect Options | From Right, as shown in Fig. 5.

Fig. 5

Finally, set the timing of the animation. In the "Timing" section of the Animations ribbon, set the following:
Start: With Previous
Duration: Set to the same duration as the slide timing
Delay: 0

These are shown in Fig. 6.

Fig. 6

Step 4: Test your Transition

Press SHIFT+F5 to run this slide with the transition. You should see the rectangle slowly disappear from the right and completely disappear as the slide transitions to the next slide. Figures 7a, 7b, and 7c illustrate this.

Fig. 7a

Fig. 7b

Fig. 7c

Step 5: Copy Shape to Other Slides

When you are satisfied that the animation is working properly, copy / paste this shape to your other slides. The animations will copy along with the shape.